diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index b6eb1d2f7..db5ea1cdb 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -83,31 +83,31 @@ impl BlockProcessingOutcome {
     }
 }
 
-pub struct BeaconChain<T: ClientDB + Sized, U: SlotClock, F: ForkChoice, B: EthSpec> {
+pub struct BeaconChain<T: ClientDB + Sized, U: SlotClock, F: ForkChoice, E: EthSpec> {
     pub block_store: Arc<BeaconBlockStore<T>>,
     pub state_store: Arc<BeaconStateStore<T>>,
     pub slot_clock: U,
-    pub op_pool: OperationPool<B>,
-    canonical_head: RwLock<CheckPoint<B>>,
-    finalized_head: RwLock<CheckPoint<B>>,
-    pub state: RwLock<BeaconState<B>>,
+    pub op_pool: OperationPool<E>,
+    canonical_head: RwLock<CheckPoint<E>>,
+    finalized_head: RwLock<CheckPoint<E>>,
+    pub state: RwLock<BeaconState<E>>,
     pub spec: ChainSpec,
     pub fork_choice: RwLock<F>,
 }
 
-impl<T, U, F, B> BeaconChain<T, U, F, B>
+impl<T, U, F, E> BeaconChain<T, U, F, E>
 where
     T: ClientDB,
     U: SlotClock,
     F: ForkChoice,
-    B: EthSpec,
+    E: EthSpec,
 {
     /// Instantiate a new Beacon Chain, from genesis.
     pub fn from_genesis(
         state_store: Arc<BeaconStateStore<T>>,
         block_store: Arc<BeaconBlockStore<T>>,
         slot_clock: U,
-        mut genesis_state: BeaconState<B>,
+        mut genesis_state: BeaconState<E>,
         genesis_block: BeaconBlock,
         spec: ChainSpec,
         fork_choice: F,
@@ -230,7 +230,7 @@ where
                 Err(BeaconStateError::SlotOutOfBounds) => {
                     // Read the earliest historic state in the current slot.
                     let earliest_historic_slot =
-                        state.slot - Slot::from(B::SlotsPerHistoricalRoot::to_usize());
+                        state.slot - Slot::from(E::SlotsPerHistoricalRoot::to_usize());
                     // Load the earlier state from disk.
                     let new_state_root = state.get_state_root(earliest_historic_slot)?;
 
@@ -270,7 +270,7 @@ where
         &self,
         new_beacon_block: BeaconBlock,
         new_beacon_block_root: Hash256,
-        new_beacon_state: BeaconState<B>,
+        new_beacon_state: BeaconState<E>,
         new_beacon_state_root: Hash256,
     ) {
         debug!(
@@ -292,7 +292,7 @@ where
     /// It is important to note that the `beacon_state` returned may not match the present slot. It
     /// is the state as it was when the head block was received, which could be some slots prior to
     /// now.
-    pub fn head(&self) -> RwLockReadGuard<CheckPoint<B>> {
+    pub fn head(&self) -> RwLockReadGuard<CheckPoint<E>> {
         self.canonical_head.read()
     }
 
@@ -302,7 +302,7 @@ where
     /// state and calling `catchup_state` as it will not result in an old state being installed and
     /// then having it iteratively updated -- in such a case it's possible for another thread to
     /// find the state at an old slot.
-    pub fn update_state(&self, mut state: BeaconState<B>) -> Result<(), Error> {
+    pub fn update_state(&self, mut state: BeaconState<E>) -> Result<(), Error> {
         let present_slot = match self.slot_clock.present_slot() {
             Ok(Some(slot)) => slot,
             _ => return Err(Error::UnableToReadSlot),
@@ -357,7 +357,7 @@ where
         &self,
         new_beacon_block: BeaconBlock,
         new_beacon_block_root: Hash256,
-        new_beacon_state: BeaconState<B>,
+        new_beacon_state: BeaconState<E>,
         new_beacon_state_root: Hash256,
     ) {
         let mut finalized_head = self.finalized_head.write();
@@ -371,7 +371,7 @@ where
 
     /// Returns a read-lock guarded `CheckPoint` struct for reading the justified head (as chosen,
     /// indirectly,  by the fork-choice rule).
-    pub fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<B>> {
+    pub fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<E>> {
         self.finalized_head.read()
     }
 
@@ -664,7 +664,7 @@ where
     pub fn produce_block(
         &self,
         randao_reveal: Signature,
-    ) -> Result<(BeaconBlock, BeaconState<B>), BlockProductionError> {
+    ) -> Result<(BeaconBlock, BeaconState<E>), BlockProductionError> {
         debug!("Producing block at slot {}...", self.state.read().slot);
 
         let mut state = self.state.read().clone();
@@ -759,7 +759,7 @@ where
     ///
     /// This could be a very expensive operation and should only be done in testing/analysis
     /// activities.
-    pub fn chain_dump(&self) -> Result<Vec<CheckPoint<B>>, Error> {
+    pub fn chain_dump(&self) -> Result<Vec<CheckPoint<E>>, Error> {
         let mut dump = vec![];
 
         let mut last_slot = CheckPoint {
diff --git a/beacon_node/beacon_chain/src/checkpoint.rs b/beacon_node/beacon_chain/src/checkpoint.rs
index 7bed5b5ce..c069ac104 100644
--- a/beacon_node/beacon_chain/src/checkpoint.rs
+++ b/beacon_node/beacon_chain/src/checkpoint.rs
@@ -4,19 +4,19 @@ use types::{BeaconBlock, BeaconState, EthSpec, Hash256};
 /// Represents some block and it's associated state. Generally, this will be used for tracking the
 /// head, justified head and finalized head.
 #[derive(Clone, Serialize, PartialEq, Debug)]
-pub struct CheckPoint<B: EthSpec> {
+pub struct CheckPoint<E: EthSpec> {
     pub beacon_block: BeaconBlock,
     pub beacon_block_root: Hash256,
-    pub beacon_state: BeaconState<B>,
+    pub beacon_state: BeaconState<E>,
     pub beacon_state_root: Hash256,
 }
 
-impl<B: EthSpec> CheckPoint<B> {
+impl<E: EthSpec> CheckPoint<E> {
     /// Create a new checkpoint.
     pub fn new(
         beacon_block: BeaconBlock,
         beacon_block_root: Hash256,
-        beacon_state: BeaconState<B>,
+        beacon_state: BeaconState<E>,
         beacon_state_root: Hash256,
     ) -> Self {
         Self {
@@ -32,7 +32,7 @@ impl<B: EthSpec> CheckPoint<B> {
         &mut self,
         beacon_block: BeaconBlock,
         beacon_block_root: Hash256,
-        beacon_state: BeaconState<B>,
+        beacon_state: BeaconState<E>,
         beacon_state_root: Hash256,
     ) {
         self.beacon_block = beacon_block;
diff --git a/beacon_node/beacon_chain/src/test_utils/testing_beacon_chain_builder.rs b/beacon_node/beacon_chain/src/test_utils/testing_beacon_chain_builder.rs
index b617ed0d7..f7ff3cdae 100644
--- a/beacon_node/beacon_chain/src/test_utils/testing_beacon_chain_builder.rs
+++ b/beacon_node/beacon_chain/src/test_utils/testing_beacon_chain_builder.rs
@@ -10,15 +10,15 @@ use tree_hash::TreeHash;
 use types::*;
 use types::{test_utils::TestingBeaconStateBuilder, EthSpec, FewValidatorsEthSpec};
 
-type TestingBeaconChain<B> =
-    BeaconChain<MemoryDB, TestingSlotClock, BitwiseLMDGhost<MemoryDB, FewValidatorsEthSpec>, B>;
+type TestingBeaconChain<E> =
+    BeaconChain<MemoryDB, TestingSlotClock, BitwiseLMDGhost<MemoryDB, FewValidatorsEthSpec>, E>;
 
-pub struct TestingBeaconChainBuilder<B: EthSpec> {
-    state_builder: TestingBeaconStateBuilder<B>,
+pub struct TestingBeaconChainBuilder<E: EthSpec> {
+    state_builder: TestingBeaconStateBuilder<E>,
 }
 
-impl<B: EthSpec> TestingBeaconChainBuilder<B> {
-    pub fn build(self, spec: &ChainSpec) -> TestingBeaconChain<B> {
+impl<E: EthSpec> TestingBeaconChainBuilder<E> {
+    pub fn build(self, spec: &ChainSpec) -> TestingBeaconChain<E> {
         let db = Arc::new(MemoryDB::open());
         let block_store = Arc::new(BeaconBlockStore::new(db.clone()));
         let state_store = Arc::new(BeaconStateStore::new(db.clone()));
@@ -44,8 +44,8 @@ impl<B: EthSpec> TestingBeaconChainBuilder<B> {
     }
 }
 
-impl<B: EthSpec> From<TestingBeaconStateBuilder<B>> for TestingBeaconChainBuilder<B> {
-    fn from(state_builder: TestingBeaconStateBuilder<B>) -> TestingBeaconChainBuilder<B> {
+impl<E: EthSpec> From<TestingBeaconStateBuilder<E>> for TestingBeaconChainBuilder<E> {
+    fn from(state_builder: TestingBeaconStateBuilder<E>) -> TestingBeaconChainBuilder<E> {
         TestingBeaconChainBuilder { state_builder }
     }
 }
diff --git a/beacon_node/client/src/lib.rs b/beacon_node/client/src/lib.rs
index 166f1a948..5d7c221ef 100644
--- a/beacon_node/client/src/lib.rs
+++ b/beacon_node/client/src/lib.rs
@@ -144,12 +144,12 @@ impl<TClientType: ClientTypes> Client<TClientType> {
     }
 }
 
-fn do_state_catchup<T, U, F, B>(chain: &Arc<BeaconChain<T, U, F, B>>, log: &slog::Logger)
+fn do_state_catchup<T, U, F, E>(chain: &Arc<BeaconChain<T, U, F, E>>, log: &slog::Logger)
 where
     T: ClientDB,
     U: SlotClock,
     F: ForkChoice,
-    B: EthSpec,
+    E: EthSpec,
 {
     if let Some(genesis_height) = chain.slots_since_genesis() {
         let result = chain.catchup_state();
diff --git a/beacon_node/db/src/stores/beacon_state_store.rs b/beacon_node/db/src/stores/beacon_state_store.rs
index c0d37edd9..1b088e4a9 100644
--- a/beacon_node/db/src/stores/beacon_state_store.rs
+++ b/beacon_node/db/src/stores/beacon_state_store.rs
@@ -19,14 +19,14 @@ impl<T: ClientDB> BeaconStateStore<T> {
         Self { db }
     }
 
-    pub fn get_deserialized<B: EthSpec>(
+    pub fn get_deserialized<E: EthSpec>(
         &self,
         hash: &Hash256,
-    ) -> Result<Option<BeaconState<B>>, DBError> {
+    ) -> Result<Option<BeaconState<E>>, DBError> {
         match self.get(&hash)? {
             None => Ok(None),
             Some(ssz) => {
-                let state = decode::<BeaconState<B>>(&ssz).map_err(|_| DBError {
+                let state = decode::<BeaconState<E>>(&ssz).map_err(|_| DBError {
                     message: "Bad State SSZ.".to_string(),
                 })?;
                 Ok(Some(state))
diff --git a/beacon_node/network/src/beacon_chain.rs b/beacon_node/network/src/beacon_chain.rs
index db809086a..a98aa73de 100644
--- a/beacon_node/network/src/beacon_chain.rs
+++ b/beacon_node/network/src/beacon_chain.rs
@@ -15,14 +15,14 @@ use types::{
 pub use beacon_chain::{BeaconChainError, BlockProcessingOutcome, InvalidBlock};
 
 /// The network's API to the beacon chain.
-pub trait BeaconChain<B: EthSpec>: Send + Sync {
+pub trait BeaconChain<E: EthSpec>: Send + Sync {
     fn get_spec(&self) -> &ChainSpec;
 
-    fn get_state(&self) -> RwLockReadGuard<BeaconState<B>>;
+    fn get_state(&self) -> RwLockReadGuard<BeaconState<E>>;
 
     fn slot(&self) -> Slot;
 
-    fn head(&self) -> RwLockReadGuard<CheckPoint<B>>;
+    fn head(&self) -> RwLockReadGuard<CheckPoint<E>>;
 
     fn get_block(&self, block_root: &Hash256) -> Result<Option<BeaconBlock>, BeaconChainError>;
 
@@ -30,7 +30,7 @@ pub trait BeaconChain<B: EthSpec>: Send + Sync {
 
     fn best_block_root(&self) -> Hash256;
 
-    fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<B>>;
+    fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<E>>;
 
     fn finalized_epoch(&self) -> Epoch;
 
@@ -64,18 +64,18 @@ pub trait BeaconChain<B: EthSpec>: Send + Sync {
     fn is_new_block_root(&self, beacon_block_root: &Hash256) -> Result<bool, BeaconChainError>;
 }
 
-impl<T, U, F, B> BeaconChain<B> for RawBeaconChain<T, U, F, B>
+impl<T, U, F, E> BeaconChain<E> for RawBeaconChain<T, U, F, E>
 where
     T: ClientDB + Sized,
     U: SlotClock,
     F: ForkChoice,
-    B: EthSpec,
+    E: EthSpec,
 {
     fn get_spec(&self) -> &ChainSpec {
         &self.spec
     }
 
-    fn get_state(&self) -> RwLockReadGuard<BeaconState<B>> {
+    fn get_state(&self) -> RwLockReadGuard<BeaconState<E>> {
         self.state.read()
     }
 
@@ -83,7 +83,7 @@ where
         self.get_state().slot
     }
 
-    fn head(&self) -> RwLockReadGuard<CheckPoint<B>> {
+    fn head(&self) -> RwLockReadGuard<CheckPoint<E>> {
         self.head()
     }
 
@@ -95,7 +95,7 @@ where
         self.get_state().finalized_epoch
     }
 
-    fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<B>> {
+    fn finalized_head(&self) -> RwLockReadGuard<CheckPoint<E>> {
         self.finalized_head()
     }
 
diff --git a/beacon_node/network/src/message_handler.rs b/beacon_node/network/src/message_handler.rs
index 35743fe15..a7d0ff2a1 100644
--- a/beacon_node/network/src/message_handler.rs
+++ b/beacon_node/network/src/message_handler.rs
@@ -21,11 +21,11 @@ use types::EthSpec;
 // const HELLO_TIMEOUT: Duration = Duration::from_secs(30);
 
 /// Handles messages received from the network and client and organises syncing.
-pub struct MessageHandler<B: EthSpec> {
+pub struct MessageHandler<E: EthSpec> {
     /// Currently loaded and initialised beacon chain.
-    _chain: Arc<BeaconChain<B>>,
+    _chain: Arc<BeaconChain<E>>,
     /// The syncing framework.
-    sync: SimpleSync<B>,
+    sync: SimpleSync<E>,
     /// The context required to send messages to, and process messages from peers.
     network_context: NetworkContext,
     /// The `MessageHandler` logger.
@@ -45,10 +45,10 @@ pub enum HandlerMessage {
     PubsubMessage(PeerId, Box<PubsubMessage>),
 }
 
-impl<B: EthSpec> MessageHandler<B> {
+impl<E: EthSpec> MessageHandler<E> {
     /// Initializes and runs the MessageHandler.
     pub fn spawn(
-        beacon_chain: Arc<BeaconChain<B>>,
+        beacon_chain: Arc<BeaconChain<E>>,
         network_send: crossbeam_channel::Sender<NetworkMessage>,
         executor: &tokio::runtime::TaskExecutor,
         log: slog::Logger,
diff --git a/beacon_node/network/src/service.rs b/beacon_node/network/src/service.rs
index 89d1e1526..50454a875 100644
--- a/beacon_node/network/src/service.rs
+++ b/beacon_node/network/src/service.rs
@@ -16,17 +16,17 @@ use tokio::runtime::TaskExecutor;
 use types::{EthSpec, Topic};
 
 /// Service that handles communication between internal services and the eth2_libp2p network service.
-pub struct Service<B: EthSpec> {
+pub struct Service<E: EthSpec> {
     //libp2p_service: Arc<Mutex<LibP2PService>>,
     _libp2p_exit: oneshot::Sender<()>,
     network_send: crossbeam_channel::Sender<NetworkMessage>,
-    _phantom: PhantomData<B>, //message_handler: MessageHandler,
+    _phantom: PhantomData<E>, //message_handler: MessageHandler,
                               //message_handler_send: Sender<HandlerMessage>
 }
 
-impl<B: EthSpec> Service<B> {
+impl<E: EthSpec> Service<E> {
     pub fn new(
-        beacon_chain: Arc<BeaconChain<B>>,
+        beacon_chain: Arc<BeaconChain<E>>,
         config: &NetworkConfig,
         executor: &TaskExecutor,
         log: slog::Logger,
diff --git a/beacon_node/network/src/sync/import_queue.rs b/beacon_node/network/src/sync/import_queue.rs
index 1fffd8763..6c2fc33ee 100644
--- a/beacon_node/network/src/sync/import_queue.rs
+++ b/beacon_node/network/src/sync/import_queue.rs
@@ -19,8 +19,8 @@ use types::{BeaconBlock, BeaconBlockBody, BeaconBlockHeader, EthSpec, Hash256, S
 /// `BeaconBlockBody` as the key.
 /// - It is possible for multiple distinct blocks to have identical `BeaconBlockBodies`. Therefore
 /// we cannot use a `HashMap` keyed by the root of `BeaconBlockBody`.
-pub struct ImportQueue<B: EthSpec> {
-    pub chain: Arc<BeaconChain<B>>,
+pub struct ImportQueue<E: EthSpec> {
+    pub chain: Arc<BeaconChain<E>>,
     /// Partially imported blocks, keyed by the root of `BeaconBlockBody`.
     pub partials: Vec<PartialBeaconBlock>,
     /// Time before a queue entry is considered state.
@@ -29,9 +29,9 @@ pub struct ImportQueue<B: EthSpec> {
     log: slog::Logger,
 }
 
-impl<B: EthSpec> ImportQueue<B> {
+impl<E: EthSpec> ImportQueue<E> {
     /// Return a new, empty queue.
-    pub fn new(chain: Arc<BeaconChain<B>>, stale_time: Duration, log: slog::Logger) -> Self {
+    pub fn new(chain: Arc<BeaconChain<E>>, stale_time: Duration, log: slog::Logger) -> Self {
         Self {
             chain,
             partials: vec![],
diff --git a/beacon_node/network/src/sync/simple_sync.rs b/beacon_node/network/src/sync/simple_sync.rs
index 3f4fb7aae..d44ffd4b7 100644
--- a/beacon_node/network/src/sync/simple_sync.rs
+++ b/beacon_node/network/src/sync/simple_sync.rs
@@ -88,8 +88,8 @@ impl From<HelloMessage> for PeerSyncInfo {
     }
 }
 
-impl<B: EthSpec> From<&Arc<BeaconChain<B>>> for PeerSyncInfo {
-    fn from(chain: &Arc<BeaconChain<B>>) -> PeerSyncInfo {
+impl<E: EthSpec> From<&Arc<BeaconChain<E>>> for PeerSyncInfo {
+    fn from(chain: &Arc<BeaconChain<E>>) -> PeerSyncInfo {
         Self::from(chain.hello_message())
     }
 }
@@ -103,22 +103,22 @@ pub enum SyncState {
 }
 
 /// Simple Syncing protocol.
-pub struct SimpleSync<B: EthSpec> {
+pub struct SimpleSync<E: EthSpec> {
     /// A reference to the underlying beacon chain.
-    chain: Arc<BeaconChain<B>>,
+    chain: Arc<BeaconChain<E>>,
     /// A mapping of Peers to their respective PeerSyncInfo.
     known_peers: HashMap<PeerId, PeerSyncInfo>,
     /// A queue to allow importing of blocks
-    import_queue: ImportQueue<B>,
+    import_queue: ImportQueue<E>,
     /// The current state of the syncing protocol.
     state: SyncState,
     /// Sync logger.
     log: slog::Logger,
 }
 
-impl<B: EthSpec> SimpleSync<B> {
+impl<E: EthSpec> SimpleSync<E> {
     /// Instantiate a `SimpleSync` instance, with no peers and an empty queue.
-    pub fn new(beacon_chain: Arc<BeaconChain<B>>, log: &slog::Logger) -> Self {
+    pub fn new(beacon_chain: Arc<BeaconChain<E>>, log: &slog::Logger) -> Self {
         let sync_logger = log.new(o!("Service"=> "Sync"));
 
         let queue_item_stale_time = Duration::from_secs(QUEUE_STALE_SECS);
diff --git a/beacon_node/rpc/src/attestation.rs b/beacon_node/rpc/src/attestation.rs
index 30f04afba..5b6d93a95 100644
--- a/beacon_node/rpc/src/attestation.rs
+++ b/beacon_node/rpc/src/attestation.rs
@@ -12,12 +12,12 @@ use std::sync::Arc;
 use types::{Attestation, EthSpec};
 
 #[derive(Clone)]
-pub struct AttestationServiceInstance<B: EthSpec> {
-    pub chain: Arc<BeaconChain<B>>,
+pub struct AttestationServiceInstance<E: EthSpec> {
+    pub chain: Arc<BeaconChain<E>>,
     pub log: slog::Logger,
 }
 
-impl<B: EthSpec> AttestationService for AttestationServiceInstance<B> {
+impl<E: EthSpec> AttestationService for AttestationServiceInstance<E> {
     /// Produce the `AttestationData` for signing by a validator.
     fn produce_attestation_data(
         &mut self,
diff --git a/beacon_node/rpc/src/beacon_block.rs b/beacon_node/rpc/src/beacon_block.rs
index 727da9542..370dce60d 100644
--- a/beacon_node/rpc/src/beacon_block.rs
+++ b/beacon_node/rpc/src/beacon_block.rs
@@ -16,13 +16,13 @@ use std::sync::Arc;
 use types::{BeaconBlock, EthSpec, Signature, Slot};
 
 #[derive(Clone)]
-pub struct BeaconBlockServiceInstance<B: EthSpec> {
-    pub chain: Arc<BeaconChain<B>>,
+pub struct BeaconBlockServiceInstance<E: EthSpec> {
+    pub chain: Arc<BeaconChain<E>>,
     pub network_chan: crossbeam_channel::Sender<NetworkMessage>,
     pub log: Logger,
 }
 
-impl<B: EthSpec> BeaconBlockService for BeaconBlockServiceInstance<B> {
+impl<E: EthSpec> BeaconBlockService for BeaconBlockServiceInstance<E> {
     /// Produce a `BeaconBlock` for signing by a validator.
     fn produce_beacon_block(
         &mut self,
diff --git a/beacon_node/rpc/src/beacon_chain.rs b/beacon_node/rpc/src/beacon_chain.rs
index e10522d04..7e75b32ce 100644
--- a/beacon_node/rpc/src/beacon_chain.rs
+++ b/beacon_node/rpc/src/beacon_chain.rs
@@ -11,12 +11,12 @@ pub use beacon_chain::{BeaconChainError, BlockProcessingOutcome};
 use types::{Attestation, AttestationData, BeaconBlock, EthSpec};
 
 /// The RPC's API to the beacon chain.
-pub trait BeaconChain<B: EthSpec>: Send + Sync {
+pub trait BeaconChain<E: EthSpec>: Send + Sync {
     fn get_spec(&self) -> &ChainSpec;
 
-    fn get_state(&self) -> RwLockReadGuard<BeaconState<B>>;
+    fn get_state(&self) -> RwLockReadGuard<BeaconState<E>>;
 
-    fn get_mut_state(&self) -> RwLockWriteGuard<BeaconState<B>>;
+    fn get_mut_state(&self) -> RwLockWriteGuard<BeaconState<E>>;
 
     fn process_block(&self, block: BeaconBlock)
         -> Result<BlockProcessingOutcome, BeaconChainError>;
@@ -24,7 +24,7 @@ pub trait BeaconChain<B: EthSpec>: Send + Sync {
     fn produce_block(
         &self,
         randao_reveal: Signature,
-    ) -> Result<(BeaconBlock, BeaconState<B>), BlockProductionError>;
+    ) -> Result<(BeaconBlock, BeaconState<E>), BlockProductionError>;
 
     fn produce_attestation_data(&self, shard: u64) -> Result<AttestationData, BeaconChainError>;
 
@@ -34,22 +34,22 @@ pub trait BeaconChain<B: EthSpec>: Send + Sync {
     ) -> Result<(), AttestationValidationError>;
 }
 
-impl<T, U, F, B> BeaconChain<B> for RawBeaconChain<T, U, F, B>
+impl<T, U, F, E> BeaconChain<E> for RawBeaconChain<T, U, F, E>
 where
     T: ClientDB + Sized,
     U: SlotClock,
     F: ForkChoice,
-    B: EthSpec,
+    E: EthSpec,
 {
     fn get_spec(&self) -> &ChainSpec {
         &self.spec
     }
 
-    fn get_state(&self) -> RwLockReadGuard<BeaconState<B>> {
+    fn get_state(&self) -> RwLockReadGuard<BeaconState<E>> {
         self.state.read()
     }
 
-    fn get_mut_state(&self) -> RwLockWriteGuard<BeaconState<B>> {
+    fn get_mut_state(&self) -> RwLockWriteGuard<BeaconState<E>> {
         self.state.write()
     }
 
@@ -63,7 +63,7 @@ where
     fn produce_block(
         &self,
         randao_reveal: Signature,
-    ) -> Result<(BeaconBlock, BeaconState<B>), BlockProductionError> {
+    ) -> Result<(BeaconBlock, BeaconState<E>), BlockProductionError> {
         self.produce_block(randao_reveal)
     }
 
diff --git a/beacon_node/rpc/src/beacon_node.rs b/beacon_node/rpc/src/beacon_node.rs
index 873d1c478..2ca39ae51 100644
--- a/beacon_node/rpc/src/beacon_node.rs
+++ b/beacon_node/rpc/src/beacon_node.rs
@@ -8,12 +8,12 @@ use std::sync::Arc;
 use types::EthSpec;
 
 #[derive(Clone)]
-pub struct BeaconNodeServiceInstance<B: EthSpec> {
-    pub chain: Arc<BeaconChain<B>>,
+pub struct BeaconNodeServiceInstance<E: EthSpec> {
+    pub chain: Arc<BeaconChain<E>>,
     pub log: slog::Logger,
 }
 
-impl<B: EthSpec> BeaconNodeService for BeaconNodeServiceInstance<B> {
+impl<E: EthSpec> BeaconNodeService for BeaconNodeServiceInstance<E> {
     /// Provides basic node information.
     fn info(&mut self, ctx: RpcContext, _req: Empty, sink: UnarySink<NodeInfoResponse>) {
         trace!(self.log, "Node info requested via RPC");
diff --git a/beacon_node/rpc/src/lib.rs b/beacon_node/rpc/src/lib.rs
index d46dee7b5..f1d5e9c88 100644
--- a/beacon_node/rpc/src/lib.rs
+++ b/beacon_node/rpc/src/lib.rs
@@ -23,11 +23,11 @@ use std::sync::Arc;
 use tokio::runtime::TaskExecutor;
 use types::EthSpec;
 
-pub fn start_server<B: EthSpec>(
+pub fn start_server<E: EthSpec>(
     config: &RPCConfig,
     executor: &TaskExecutor,
     network_chan: crossbeam_channel::Sender<NetworkMessage>,
-    beacon_chain: Arc<BeaconChain<B>>,
+    beacon_chain: Arc<BeaconChain<E>>,
     log: &slog::Logger,
 ) -> exit_future::Signal {
     let log = log.new(o!("Service"=>"RPC"));
diff --git a/beacon_node/rpc/src/validator.rs b/beacon_node/rpc/src/validator.rs
index e2f8d098f..6a145d32d 100644
--- a/beacon_node/rpc/src/validator.rs
+++ b/beacon_node/rpc/src/validator.rs
@@ -10,13 +10,13 @@ use std::sync::Arc;
 use types::{Epoch, EthSpec, RelativeEpoch};
 
 #[derive(Clone)]
-pub struct ValidatorServiceInstance<B: EthSpec> {
-    pub chain: Arc<BeaconChain<B>>,
+pub struct ValidatorServiceInstance<E: EthSpec> {
+    pub chain: Arc<BeaconChain<E>>,
     pub log: slog::Logger,
 }
 //TODO: Refactor Errors
 
-impl<B: EthSpec> ValidatorService for ValidatorServiceInstance<B> {
+impl<E: EthSpec> ValidatorService for ValidatorServiceInstance<E> {
     /// For a list of validator public keys, this function returns the slot at which each
     /// validator must propose a block, attest to a shard, their shard committee and the shard they
     /// need to attest to.
diff --git a/eth2/fork_choice/src/bitwise_lmd_ghost.rs b/eth2/fork_choice/src/bitwise_lmd_ghost.rs
index 3eb8bff8c..0bbac6bb6 100644
--- a/eth2/fork_choice/src/bitwise_lmd_ghost.rs
+++ b/eth2/fork_choice/src/bitwise_lmd_ghost.rs
@@ -34,7 +34,7 @@ fn power_of_2_below(x: u64) -> u64 {
 }
 
 /// Stores the necessary data structures to run the optimised bitwise lmd ghost algorithm.
-pub struct BitwiseLMDGhost<T: ClientDB + Sized, B> {
+pub struct BitwiseLMDGhost<T: ClientDB + Sized, E> {
     /// A cache of known ancestors at given heights for a specific block.
     //TODO: Consider FnvHashMap
     cache: HashMap<CacheKey<u64>, Hash256>,
@@ -51,10 +51,10 @@ pub struct BitwiseLMDGhost<T: ClientDB + Sized, B> {
     /// State storage access.
     state_store: Arc<BeaconStateStore<T>>,
     max_known_height: SlotHeight,
-    _phantom: PhantomData<B>,
+    _phantom: PhantomData<E>,
 }
 
-impl<T, B: EthSpec> BitwiseLMDGhost<T, B>
+impl<T, E: EthSpec> BitwiseLMDGhost<T, E>
 where
     T: ClientDB + Sized,
 {
@@ -88,7 +88,7 @@ where
         // build a hashmap of block_hash to weighted votes
         let mut latest_votes: HashMap<Hash256, u64> = HashMap::new();
         // gets the current weighted votes
-        let current_state: BeaconState<B> = self
+        let current_state: BeaconState<E> = self
             .state_store
             .get_deserialized(&state_root)?
             .ok_or_else(|| ForkChoiceError::MissingBeaconState(*state_root))?;
@@ -243,7 +243,7 @@ where
     }
 }
 
-impl<T: ClientDB + Sized, B: EthSpec> ForkChoice for BitwiseLMDGhost<T, B> {
+impl<T: ClientDB + Sized, E: EthSpec> ForkChoice for BitwiseLMDGhost<T, E> {
     fn add_block(
         &mut self,
         block: &BeaconBlock,
diff --git a/eth2/fork_choice/src/optimized_lmd_ghost.rs b/eth2/fork_choice/src/optimized_lmd_ghost.rs
index a471452c8..3f585e3c1 100644
--- a/eth2/fork_choice/src/optimized_lmd_ghost.rs
+++ b/eth2/fork_choice/src/optimized_lmd_ghost.rs
@@ -34,7 +34,7 @@ fn power_of_2_below(x: u64) -> u64 {
 }
 
 /// Stores the necessary data structures to run the optimised lmd ghost algorithm.
-pub struct OptimizedLMDGhost<T: ClientDB + Sized, B> {
+pub struct OptimizedLMDGhost<T: ClientDB + Sized, E> {
     /// A cache of known ancestors at given heights for a specific block.
     //TODO: Consider FnvHashMap
     cache: HashMap<CacheKey<u64>, Hash256>,
@@ -51,10 +51,10 @@ pub struct OptimizedLMDGhost<T: ClientDB + Sized, B> {
     /// State storage access.
     state_store: Arc<BeaconStateStore<T>>,
     max_known_height: SlotHeight,
-    _phantom: PhantomData<B>,
+    _phantom: PhantomData<E>,
 }
 
-impl<T, B: EthSpec> OptimizedLMDGhost<T, B>
+impl<T, E: EthSpec> OptimizedLMDGhost<T, E>
 where
     T: ClientDB + Sized,
 {
@@ -88,7 +88,7 @@ where
         // build a hashmap of block_hash to weighted votes
         let mut latest_votes: HashMap<Hash256, u64> = HashMap::new();
         // gets the current weighted votes
-        let current_state: BeaconState<B> = self
+        let current_state: BeaconState<E> = self
             .state_store
             .get_deserialized(&state_root)?
             .ok_or_else(|| ForkChoiceError::MissingBeaconState(*state_root))?;
@@ -214,7 +214,7 @@ where
     }
 }
 
-impl<T: ClientDB + Sized, B: EthSpec> ForkChoice for OptimizedLMDGhost<T, B> {
+impl<T: ClientDB + Sized, E: EthSpec> ForkChoice for OptimizedLMDGhost<T, E> {
     fn add_block(
         &mut self,
         block: &BeaconBlock,
diff --git a/eth2/fork_choice/src/slow_lmd_ghost.rs b/eth2/fork_choice/src/slow_lmd_ghost.rs
index c11ef3eec..c9aaa70d1 100644
--- a/eth2/fork_choice/src/slow_lmd_ghost.rs
+++ b/eth2/fork_choice/src/slow_lmd_ghost.rs
@@ -13,7 +13,7 @@ use types::{BeaconBlock, BeaconState, ChainSpec, EthSpec, Hash256, Slot};
 
 //TODO: Pruning and syncing
 
-pub struct SlowLMDGhost<T: ClientDB + Sized, B> {
+pub struct SlowLMDGhost<T: ClientDB + Sized, E> {
     /// The latest attestation targets as a map of validator index to block hash.
     //TODO: Could this be a fixed size vec
     latest_attestation_targets: HashMap<u64, Hash256>,
@@ -23,10 +23,10 @@ pub struct SlowLMDGhost<T: ClientDB + Sized, B> {
     block_store: Arc<BeaconBlockStore<T>>,
     /// State storage access.
     state_store: Arc<BeaconStateStore<T>>,
-    _phantom: PhantomData<B>,
+    _phantom: PhantomData<E>,
 }
 
-impl<T, B: EthSpec> SlowLMDGhost<T, B>
+impl<T, E: EthSpec> SlowLMDGhost<T, E>
 where
     T: ClientDB + Sized,
 {
@@ -57,7 +57,7 @@ where
         // build a hashmap of block_hash to weighted votes
         let mut latest_votes: HashMap<Hash256, u64> = HashMap::new();
         // gets the current weighted votes
-        let current_state: BeaconState<B> = self
+        let current_state: BeaconState<E> = self
             .state_store
             .get_deserialized(&state_root)?
             .ok_or_else(|| ForkChoiceError::MissingBeaconState(*state_root))?;
@@ -108,7 +108,7 @@ where
     }
 }
 
-impl<T: ClientDB + Sized, B: EthSpec> ForkChoice for SlowLMDGhost<T, B> {
+impl<T: ClientDB + Sized, E: EthSpec> ForkChoice for SlowLMDGhost<T, E> {
     /// Process when a block is added
     fn add_block(
         &mut self,
diff --git a/eth2/operation_pool/src/lib.rs b/eth2/operation_pool/src/lib.rs
index cbaabe0cd..c5653e7f9 100644
--- a/eth2/operation_pool/src/lib.rs
+++ b/eth2/operation_pool/src/lib.rs
@@ -539,10 +539,10 @@ where
 /// The keys in the map should be validator indices, which will be looked up
 /// in the state's validator registry and then passed to `prune_if`.
 /// Entries for unknown validators will be kept.
-fn prune_validator_hash_map<T, F, B: EthSpec>(
+fn prune_validator_hash_map<T, F, E: EthSpec>(
     map: &mut HashMap<u64, T>,
     prune_if: F,
-    finalized_state: &BeaconState<B>,
+    finalized_state: &BeaconState<E>,
 ) where
     F: Fn(&Validator) -> bool,
 {
@@ -722,12 +722,12 @@ mod tests {
 
         /// Create a signed attestation for use in tests.
         /// Signed by all validators in `committee[signing_range]` and `committee[extra_signer]`.
-        fn signed_attestation<R: std::slice::SliceIndex<[usize], Output = [usize]>, B: EthSpec>(
+        fn signed_attestation<R: std::slice::SliceIndex<[usize], Output = [usize]>, E: EthSpec>(
             committee: &CrosslinkCommittee,
             keypairs: &[Keypair],
             signing_range: R,
             slot: Slot,
-            state: &BeaconState<B>,
+            state: &BeaconState<E>,
             spec: &ChainSpec,
             extra_signer: Option<usize>,
         ) -> Attestation {
@@ -754,10 +754,10 @@ mod tests {
         }
 
         /// Test state for attestation-related tests.
-        fn attestation_test_state<B: EthSpec>(
+        fn attestation_test_state<E: EthSpec>(
             num_committees: usize,
-        ) -> (BeaconState<B>, Vec<Keypair>, ChainSpec) {
-            let spec = B::spec();
+        ) -> (BeaconState<E>, Vec<Keypair>, ChainSpec) {
+            let spec = E::spec();
 
             let num_validators =
                 num_committees * (spec.slots_per_epoch * spec.target_committee_size) as usize;
@@ -775,9 +775,9 @@ mod tests {
         }
 
         /// Set the latest crosslink in the state to match the attestation.
-        fn fake_latest_crosslink<B: EthSpec>(
+        fn fake_latest_crosslink<E: EthSpec>(
             att: &Attestation,
-            state: &mut BeaconState<B>,
+            state: &mut BeaconState<E>,
             spec: &ChainSpec,
         ) {
             state.latest_crosslinks[att.data.shard as usize] = Crosslink {