diff --git a/eth2/types/src/attestation.rs b/eth2/types/src/attestation.rs
index f1fed9d27..682716073 100644
--- a/eth2/types/src/attestation.rs
+++ b/eth2/types/src/attestation.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// Details an attestation that can be slashable.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/attestation_data.rs b/eth2/types/src/attestation_data.rs
index 5a7a0dc62..3b0f529d6 100644
--- a/eth2/types/src/attestation_data.rs
+++ b/eth2/types/src/attestation_data.rs
@@ -14,6 +14,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
     Debug,
     Clone,
     PartialEq,
+    Eq,
     Default,
     Serialize,
     Deserialize,
@@ -41,8 +42,6 @@ pub struct AttestationData {
     pub crosslink_data_root: Hash256,
 }
 
-impl Eq for AttestationData {}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/eth2/types/src/attester_slashing.rs b/eth2/types/src/attester_slashing.rs
index c3c064503..2b6402fcc 100644
--- a/eth2/types/src/attester_slashing.rs
+++ b/eth2/types/src/attester_slashing.rs
@@ -7,7 +7,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Two conflicting attestations.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/beacon_block.rs b/eth2/types/src/beacon_block.rs
index 3f4dfb0b0..2a829fda2 100644
--- a/eth2/types/src/beacon_block.rs
+++ b/eth2/types/src/beacon_block.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// A block of the `BeaconChain`.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
@@ -36,7 +36,7 @@ pub struct BeaconBlock {
 impl BeaconBlock {
     /// Returns an empty block to be used during genesis.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn empty(spec: &ChainSpec) -> BeaconBlock {
         BeaconBlock {
             slot: spec.genesis_slot,
@@ -49,6 +49,7 @@ impl BeaconBlock {
                     block_hash: spec.zero_hash,
                     deposit_count: 0,
                 },
+                graffiti: [0; 32],
                 proposer_slashings: vec![],
                 attester_slashings: vec![],
                 attestations: vec![],
@@ -62,7 +63,7 @@ impl BeaconBlock {
 
     /// Returns the `tree_hash_root | update` of the block.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.tree_hash_root()[..])
     }
@@ -74,7 +75,7 @@ impl BeaconBlock {
     ///
     /// Note: performs a full tree-hash of `self.body`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn block_header(&self) -> BeaconBlockHeader {
         BeaconBlockHeader {
             slot: self.slot,
@@ -87,7 +88,7 @@ impl BeaconBlock {
 
     /// Returns a "temporary" header, where the `state_root` is `spec.zero_hash`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn temporary_block_header(&self, spec: &ChainSpec) -> BeaconBlockHeader {
         BeaconBlockHeader {
             state_root: spec.zero_hash,
diff --git a/eth2/types/src/beacon_block_body.rs b/eth2/types/src/beacon_block_body.rs
index 867db78c4..8bbdbec15 100644
--- a/eth2/types/src/beacon_block_body.rs
+++ b/eth2/types/src/beacon_block_body.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// The body of a `BeaconChain` block, containing operations.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
@@ -24,6 +24,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 pub struct BeaconBlockBody {
     pub randao_reveal: Signature,
     pub eth1_data: Eth1Data,
+    pub graffiti: [u8; 32],
     pub proposer_slashings: Vec<ProposerSlashing>,
     pub attester_slashings: Vec<AttesterSlashing>,
     pub attestations: Vec<Attestation>,
diff --git a/eth2/types/src/beacon_block_header.rs b/eth2/types/src/beacon_block_header.rs
index 601346db5..f58803c20 100644
--- a/eth2/types/src/beacon_block_header.rs
+++ b/eth2/types/src/beacon_block_header.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// A header of a `BeaconBlock`.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
@@ -36,14 +36,14 @@ pub struct BeaconBlockHeader {
 impl BeaconBlockHeader {
     /// Returns the `tree_hash_root` of the header.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.signed_root()[..])
     }
 
     /// Given a `body`, consumes `self` and returns a complete `BeaconBlock`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn into_block(self, body: BeaconBlockBody) -> BeaconBlock {
         BeaconBlock {
             slot: self.slot,
diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index fd8821bd8..4c6f8d2a2 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -55,7 +55,7 @@ pub enum Error {
 
 /// The state of the `BeaconChain` at some slot.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
@@ -150,7 +150,7 @@ impl<T: EthSpec> BeaconState<T> {
     /// This does not fully build a genesis beacon state, it omits processing of initial validator
     /// deposits. To obtain a full genesis beacon state, use the `BeaconStateBuilder`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn genesis(
         genesis_time: u64,
         latest_eth1_data: Eth1Data,
@@ -229,7 +229,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Returns the `tree_hash_root` of the state.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.tree_hash_root()[..])
     }
@@ -258,7 +258,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// The epoch corresponding to `self.slot`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn current_epoch(&self, spec: &ChainSpec) -> Epoch {
         self.slot.epoch(spec.slots_per_epoch)
     }
@@ -279,7 +279,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// The epoch following `self.current_epoch()`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.1
     pub fn next_epoch(&self, spec: &ChainSpec) -> Epoch {
         self.current_epoch(spec) + 1
     }
diff --git a/eth2/types/src/crosslink.rs b/eth2/types/src/crosslink.rs
index f44d1166e..9a06ca8bf 100644
--- a/eth2/types/src/crosslink.rs
+++ b/eth2/types/src/crosslink.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Specifies the block hash for a shard at an epoch.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/deposit.rs b/eth2/types/src/deposit.rs
index 34fab4699..1b031b0d5 100644
--- a/eth2/types/src/deposit.rs
+++ b/eth2/types/src/deposit.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// A deposit to potentially become a beacon chain validator.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/deposit_data.rs b/eth2/types/src/deposit_data.rs
index e1f6d1b1d..d00bb69e2 100644
--- a/eth2/types/src/deposit_data.rs
+++ b/eth2/types/src/deposit_data.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// The data supplied by the user to the deposit contract.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/eth1_data.rs b/eth2/types/src/eth1_data.rs
index 97f37e415..0a7043543 100644
--- a/eth2/types/src/eth1_data.rs
+++ b/eth2/types/src/eth1_data.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Contains data obtained from the Eth1 chain.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/indexed_attestation.rs b/eth2/types/src/indexed_attestation.rs
index af294dfc1..14f6e470b 100644
--- a/eth2/types/src/indexed_attestation.rs
+++ b/eth2/types/src/indexed_attestation.rs
@@ -1,4 +1,4 @@
-use crate::{test_utils::TestRandom, AggregateSignature, AttestationData, Bitfield};
+use crate::{test_utils::TestRandom, AggregateSignature, AttestationData};
 use serde_derive::{Deserialize, Serialize};
 use ssz_derive::{Decode, Encode};
 use test_random_derive::TestRandom;
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 ///
 /// To be included in an `AttesterSlashing`.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
@@ -28,7 +28,6 @@ pub struct IndexedAttestation {
     pub custody_bit_0_indices: Vec<u64>,
     pub custody_bit_1_indices: Vec<u64>,
     pub data: AttestationData,
-    pub custody_bitfield: Bitfield,
     #[signed_root(skip_hashing)]
     pub signature: AggregateSignature,
 }
diff --git a/eth2/types/src/proposer_slashing.rs b/eth2/types/src/proposer_slashing.rs
index 0c419dd56..b4d5ef0e5 100644
--- a/eth2/types/src/proposer_slashing.rs
+++ b/eth2/types/src/proposer_slashing.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Two conflicting proposals from the same proposer (validator).
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/test_utils/test_random.rs b/eth2/types/src/test_utils/test_random.rs
index ceb785424..4f56d1596 100644
--- a/eth2/types/src/test_utils/test_random.rs
+++ b/eth2/types/src/test_utils/test_random.rs
@@ -81,3 +81,4 @@ macro_rules! impl_test_random_for_u8_array {
 }
 
 impl_test_random_for_u8_array!(4);
+impl_test_random_for_u8_array!(32);
diff --git a/eth2/types/src/test_utils/testing_attester_slashing_builder.rs b/eth2/types/src/test_utils/testing_attester_slashing_builder.rs
index 9a8c145de..6cde3f145 100644
--- a/eth2/types/src/test_utils/testing_attester_slashing_builder.rs
+++ b/eth2/types/src/test_utils/testing_attester_slashing_builder.rs
@@ -47,7 +47,6 @@ impl TestingAttesterSlashingBuilder {
             custody_bit_0_indices: validator_indices.to_vec(),
             custody_bit_1_indices: vec![],
             data: data_1,
-            custody_bitfield: Bitfield::new(),
             signature: AggregateSignature::new(),
         };
 
@@ -55,7 +54,6 @@ impl TestingAttesterSlashingBuilder {
             custody_bit_0_indices: validator_indices.to_vec(),
             custody_bit_1_indices: vec![],
             data: data_2,
-            custody_bitfield: Bitfield::new(),
             signature: AggregateSignature::new(),
         };
 
@@ -67,8 +65,7 @@ impl TestingAttesterSlashingBuilder {
             };
             let message = attestation_data_and_custody_bit.tree_hash_root();
 
-            for (i, validator_index) in validator_indices.iter().enumerate() {
-                attestation.custody_bitfield.set(i, false);
+            for validator_index in validator_indices {
                 let signature =
                     signer(*validator_index, &message[..], epoch_2, Domain::Attestation);
                 attestation.signature.add(&signature);
diff --git a/eth2/types/src/transfer.rs b/eth2/types/src/transfer.rs
index 176a9d75d..ffac85c7b 100644
--- a/eth2/types/src/transfer.rs
+++ b/eth2/types/src/transfer.rs
@@ -11,7 +11,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// The data submitted to the deposit contract.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/validator.rs b/eth2/types/src/validator.rs
index 437112c04..ad65a8c60 100644
--- a/eth2/types/src/validator.rs
+++ b/eth2/types/src/validator.rs
@@ -7,7 +7,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Information about a `BeaconChain` validator.
 ///
-/// Spec v0.6.0
+/// Spec v0.6.1
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/voluntary_exit.rs b/eth2/types/src/voluntary_exit.rs
index a138fb480..6754aa2c9 100644
--- a/eth2/types/src/voluntary_exit.rs
+++ b/eth2/types/src/voluntary_exit.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// An exit voluntarily submitted a validator who wishes to withdraw.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/utils/cached_tree_hash/src/impls.rs b/eth2/utils/cached_tree_hash/src/impls.rs
index 5105ad6a7..aec61f34b 100644
--- a/eth2/utils/cached_tree_hash/src/impls.rs
+++ b/eth2/utils/cached_tree_hash/src/impls.rs
@@ -60,29 +60,36 @@ impl CachedTreeHash for bool {
     }
 }
 
-impl CachedTreeHash for [u8; 4] {
-    fn new_tree_hash_cache(&self, _depth: usize) -> Result<TreeHashCache, Error> {
-        Ok(TreeHashCache::from_bytes(
-            merkleize(self.to_vec()),
-            false,
-            None,
-        )?)
-    }
+macro_rules! impl_for_u8_array {
+    ($len: expr) => {
+        impl CachedTreeHash for [u8; $len] {
+            fn new_tree_hash_cache(&self, _depth: usize) -> Result<TreeHashCache, Error> {
+                Ok(TreeHashCache::from_bytes(
+                    merkleize(self.to_vec()),
+                    false,
+                    None,
+                )?)
+            }
 
-    fn tree_hash_cache_schema(&self, depth: usize) -> BTreeSchema {
-        BTreeSchema::from_lengths(depth, vec![1])
-    }
+            fn tree_hash_cache_schema(&self, depth: usize) -> BTreeSchema {
+                BTreeSchema::from_lengths(depth, vec![1])
+            }
 
-    fn update_tree_hash_cache(&self, cache: &mut TreeHashCache) -> Result<(), Error> {
-        let leaf = merkleize(self.to_vec());
-        cache.maybe_update_chunk(cache.chunk_index, &leaf)?;
+            fn update_tree_hash_cache(&self, cache: &mut TreeHashCache) -> Result<(), Error> {
+                let leaf = merkleize(self.to_vec());
+                cache.maybe_update_chunk(cache.chunk_index, &leaf)?;
 
-        cache.chunk_index += 1;
+                cache.chunk_index += 1;
 
-        Ok(())
-    }
+                Ok(())
+            }
+        }
+    };
 }
 
+impl_for_u8_array!(4);
+impl_for_u8_array!(32);
+
 impl CachedTreeHash for H256 {
     fn new_tree_hash_cache(&self, _depth: usize) -> Result<TreeHashCache, Error> {
         Ok(TreeHashCache::from_bytes(
diff --git a/eth2/utils/ssz/src/decode/impls.rs b/eth2/utils/ssz/src/decode/impls.rs
index 8a5a36780..cecc1935e 100644
--- a/eth2/utils/ssz/src/decode/impls.rs
+++ b/eth2/utils/ssz/src/decode/impls.rs
@@ -57,7 +57,7 @@ impl Decode for bool {
                 _ => {
                     return Err(DecodeError::BytesInvalid(
                         format!("Out-of-range for boolean: {}", bytes[0]).to_string(),
-                    ))
+                    ));
                 }
             }
         }
@@ -114,6 +114,7 @@ macro_rules! impl_decodable_for_u8_array {
 }
 
 impl_decodable_for_u8_array!(4);
+impl_decodable_for_u8_array!(32);
 
 impl<T: Decode> Decode for Vec<T> {
     fn is_ssz_fixed_len() -> bool {
diff --git a/eth2/utils/ssz/src/encode/impls.rs b/eth2/utils/ssz/src/encode/impls.rs
index 07886d68f..dbe4e700a 100644
--- a/eth2/utils/ssz/src/encode/impls.rs
+++ b/eth2/utils/ssz/src/encode/impls.rs
@@ -96,6 +96,7 @@ macro_rules! impl_encodable_for_u8_array {
 }
 
 impl_encodable_for_u8_array!(4);
+impl_encodable_for_u8_array!(32);
 
 #[cfg(test)]
 mod tests {
diff --git a/eth2/utils/tree_hash/src/impls.rs b/eth2/utils/tree_hash/src/impls.rs
index 42ea9add0..212aba3c8 100644
--- a/eth2/utils/tree_hash/src/impls.rs
+++ b/eth2/utils/tree_hash/src/impls.rs
@@ -51,24 +51,31 @@ impl TreeHash for bool {
     }
 }
 
-impl TreeHash for [u8; 4] {
-    fn tree_hash_type() -> TreeHashType {
-        TreeHashType::Vector
-    }
+macro_rules! impl_for_u8_array {
+    ($len: expr) => {
+        impl TreeHash for [u8; $len] {
+            fn tree_hash_type() -> TreeHashType {
+                TreeHashType::Vector
+            }
 
-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-        unreachable!("bytesN should never be packed.")
-    }
+            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+                unreachable!("bytesN should never be packed.")
+            }
 
-    fn tree_hash_packing_factor() -> usize {
-        unreachable!("bytesN should never be packed.")
-    }
+            fn tree_hash_packing_factor() -> usize {
+                unreachable!("bytesN should never be packed.")
+            }
 
-    fn tree_hash_root(&self) -> Vec<u8> {
-        merkle_root(&self[..])
-    }
+            fn tree_hash_root(&self) -> Vec<u8> {
+                merkle_root(&self[..])
+            }
+        }
+    };
 }
 
+impl_for_u8_array!(4);
+impl_for_u8_array!(32);
+
 impl TreeHash for H256 {
     fn tree_hash_type() -> TreeHashType {
         TreeHashType::Vector