diff --git a/boolean-bitfield/Cargo.toml b/boolean-bitfield/Cargo.toml
index 6e790ea23..feacb844a 100644
--- a/boolean-bitfield/Cargo.toml
+++ b/boolean-bitfield/Cargo.toml
@@ -4,3 +4,4 @@ version = "0.1.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
 
 [dependencies]
+ssz = { path = "../ssz" }
diff --git a/boolean-bitfield/src/lib.rs b/boolean-bitfield/src/lib.rs
index da789c476..6c75e2e5e 100644
--- a/boolean-bitfield/src/lib.rs
+++ b/boolean-bitfield/src/lib.rs
@@ -15,59 +15,71 @@ pub struct BooleanBitfield{
 }
 
 impl BooleanBitfield {
+    /// Create a new bitfield with a length of zero.
     pub fn new() -> Self {
         Self {
             len: 0,
             vec: vec![]
         }
     }
-    
+
+    /// Create a new bitfield of a certain capacity
     pub fn with_capacity(capacity: usize) -> Self {
         Self {
             len: 0,
-            vec: Vec::with_capacity(capacity)
+            vec: Vec::with_capacity(capacity / 8 + 1)
         }
     }
 
-    // Output the bitfield as a big-endian vec of u8.
-    pub fn to_be_vec(&self) -> Vec<u8> {
-        let mut o = self.vec.clone();
-        o.reverse();
-        o
-    }
-
+    /// Read the value of a bit.
+    ///
+    /// Will return `true` if the bit has been set to `true`
+    /// without then being set to `False`.
     pub fn get_bit(&self, i: &usize) -> bool {
-        self.get_bit_on_byte(*i % 8, *i / 8)
-    }
+        let bit = |i: &usize| *i % 8;
+        let byte = |i: &usize| *i / 8;
 
-    fn get_bit_on_byte(&self, bit: usize, byte: usize) -> bool {
-        assert!(bit < 8);
-        if byte >= self.vec.len() {
+        if byte(i) >= self.vec.len() {
             false
         } else {
-             self.vec[byte] & (1 << (bit as u8)) != 0
+             self.vec[byte(i)] & (1 << (bit(i) as u8)) != 0
         }
     }
 
-    pub fn set_bit(&mut self, bit: &usize, to: &bool) {
-        self.len = max(self.len, *bit + 1);
-        self.set_bit_on_byte(*bit % 8, *bit / 8, to);
-    }
+    /// Set the value of a bit.
+    ///
+    /// If this bit is larger than the length of the underlying byte
+    /// array it will be extended.
+    pub fn set_bit(&mut self, i: &usize, to: &bool) {
+        let bit = |i: &usize| *i % 8;
+        let byte = |i: &usize| *i / 8;
 
-    fn set_bit_on_byte(&mut self, bit: usize, byte: usize, val: &bool) {
-        assert!(bit < 8);
-        if byte >= self.vec.len() {
-            self.vec.resize(byte + 1, 0);
+        self.len = max(self.len, i + 1);
+
+        if byte(i) >= self.vec.len() {
+            self.vec.resize(byte(i) + 1, 0);
         }
-        match val {
-            true =>  self.vec[byte] = self.vec[byte] |  (1 << (bit as u8)),
-            false => self.vec[byte] = self.vec[byte] & !(1 << (bit as u8))
+        match to {
+            true =>  {
+                self.vec[byte(i)] =
+                    self.vec[byte(i)] |  (1 << (bit(i) as u8))
+            }
+            false => {
+                self.vec[byte(i)] =
+                    self.vec[byte(i)] & !(1 << (bit(i) as u8))
+            }
         }
     }
 
+    /// Return the "length" of this bitfield. Length is defined as
+    /// the highest bit that has been set.
+    ///
+    /// Note: this is distinct from the length of the underlying
+    /// vector.
     pub fn len(&self) -> usize { self.len }
 
-    // Return the total number of bits set to true.
+    /// Iterate through the underlying vector and count the number of
+    /// true bits.
     pub fn num_true_bits(&self) -> u64 {
         let mut count: u64 = 0;
         for byte in &self.vec {
@@ -79,6 +91,13 @@ impl BooleanBitfield {
         }
         count
     }
+
+    /// Clone and return the underlying byte array (`Vec<u8>`).
+    pub fn to_vec(&self) -> Vec<u8> {
+        let mut o = self.vec.clone();
+        o.reverse();
+        o
+    }
 }
 
 impl PartialEq for BooleanBitfield {
@@ -101,49 +120,49 @@ impl Clone for BooleanBitfield {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use super::rlp;
 
     #[test]
     fn test_bitfield_set() {
         let mut b = BooleanBitfield::new();
         b.set_bit(&0, &false);
-        assert_eq!(b.to_be_vec(), [0]);
-        
+        assert_eq!(b.to_vec(), [0]);
+
         b = BooleanBitfield::new();
         b.set_bit(&7, &true);
-        assert_eq!(b.to_be_vec(), [128]);
+        assert_eq!(b.to_vec(), [128]);
         b.set_bit(&7, &false);
-        assert_eq!(b.to_be_vec(), [0]);
+        assert_eq!(b.to_vec(), [0]);
         assert_eq!(b.len(), 8);
-        
+
         b = BooleanBitfield::new();
         b.set_bit(&7, &true);
         b.set_bit(&0, &true);
-        assert_eq!(b.to_be_vec(), [129]);
+        assert_eq!(b.to_vec(), [129]);
         b.set_bit(&7, &false);
-        assert_eq!(b.to_be_vec(), [1]);
+        assert_eq!(b.to_vec(), [1]);
         assert_eq!(b.len(), 8);
-        
+
         b = BooleanBitfield::new();
         b.set_bit(&8, &true);
-        assert_eq!(b.to_be_vec(), [1, 0]);
-        b.set_bit(&8, &false);
-        assert_eq!(b.to_be_vec(), [0, 0]);
+        assert_eq!(b.to_vec(), [1, 0]);
         assert_eq!(b.len(), 9);
-        
+        b.set_bit(&8, &false);
+        assert_eq!(b.to_vec(), [0, 0]);
+        assert_eq!(b.len(), 9);
+
         b = BooleanBitfield::new();
         b.set_bit(&15, &true);
-        assert_eq!(b.to_be_vec(), [128, 0]);
+        assert_eq!(b.to_vec(), [128, 0]);
         b.set_bit(&15, &false);
-        assert_eq!(b.to_be_vec(), [0, 0]);
+        assert_eq!(b.to_vec(), [0, 0]);
         assert_eq!(b.len(), 16);
-        
+
         b = BooleanBitfield::new();
         b.set_bit(&8, &true);
         b.set_bit(&15, &true);
-        assert_eq!(b.to_be_vec(), [129, 0]);
+        assert_eq!(b.to_vec(), [129, 0]);
         b.set_bit(&15, &false);
-        assert_eq!(b.to_be_vec(), [1, 0]);
+        assert_eq!(b.to_vec(), [1, 0]);
         assert_eq!(b.len(), 16);
     }
 
@@ -156,9 +175,9 @@ mod tests {
             b.set_bit(&i, &true);
             assert_eq!(b.get_bit(&i), true);
             b.set_bit(&i, &true);
-        } 
+        }
     }
-    
+
     #[test]
     fn test_bitfield_num_true_bits() {
         let mut b = BooleanBitfield::new();
diff --git a/ssz/src/lib.rs b/ssz/src/lib.rs
index 9b392a875..f1ab50ad2 100644
--- a/ssz/src/lib.rs
+++ b/ssz/src/lib.rs
@@ -1,8 +1,8 @@
 /*
- * This is a WIP of implementing an alternative 
+ * This is a WIP of implementing an alternative
  * serialization strategy. It attempts to follow Vitalik's
- * "ssz" format here: 
- * https://github.com/ethereum/research/tree/master/py_ssz
+ * "simpleserialize" format here:
+ * https://github.com/ethereum/beacon_chain/blob/master/beacon_chain/utils/simpleserialize.py
  *
  * This implementation is not final and would almost certainly
  * have issues.
@@ -24,12 +24,14 @@ pub struct SszStream {
 }
 
 impl SszStream {
+    /// Create a new, empty steam for writing ssz values.
     pub fn new() -> Self {
         SszStream {
             buffer: Vec::new()
         }
     }
 
+    /// Append some ssz encodable value to the stream.
     pub fn append<E>(&mut self, value: &E) -> &mut Self
         where E: Encodable
     {
@@ -37,30 +39,34 @@ impl SszStream {
         self
     }
 
-    fn append_encoded_vec(&mut self, v: &mut Vec<u8>) {
-        self.buffer.append(&mut encode_length(v.len(), LENGTH_BYTES));
-        self.buffer.append(v) ;
+    pub fn extend_buffer(&mut self, vec: &mut Vec<u8>) {
+        self.buffer.append(&mut encode_length(vec.len(), LENGTH_BYTES));
+        self.buffer.append(vec);
     }
-    
-    fn append_encoded_array(&mut self, a: &mut [u8]) {
+
+    /// Append some vector (list) of encoded values to the stream.
+    pub fn append_vec<E>(&mut self, vec: &mut Vec<E>)
+        where E: Encodable
+    {
+        self.buffer.append(&mut encode_length(vec.len(), LENGTH_BYTES));
+        for v in vec {
+            v.ssz_append(self);
+        }
+    }
+
+    /// Append some array (list) of encoded values to the stream.
+    pub fn append_encoded_array(&mut self, a: &mut [u8]) {
         let len = a.len();
         self.buffer.append(&mut encode_length(len, LENGTH_BYTES));
         self.buffer.extend_from_slice(&a[0..len]);
     }
 
+    /// Consume the stream and return the underlying bytes.
     pub fn drain(self) -> Vec<u8> {
         self.buffer
     }
 }
 
-pub fn encode<E>(value: &E) -> Vec<u8>
-    where E: Encodable
-{
-    let mut stream = SszStream::new();
-    stream.append(value);
-    stream.drain()
-}
-
 fn encode_length(len: usize, length_bytes: usize) -> Vec<u8> {
     assert!(length_bytes > 0);  // For sanity
     assert!((len as usize) < 2usize.pow(length_bytes as u32 * 8));
@@ -75,12 +81,25 @@ fn encode_length(len: usize, length_bytes: usize) -> Vec<u8> {
 /*
  * Implementations for various types
  */
+impl Encodable for u8 {
+    fn ssz_append(&self, s: &mut SszStream) {
+        s.buffer.append(&mut vec![*self]);
+    }
+}
+
+impl Encodable for u16 {
+    fn ssz_append(&self, s: &mut SszStream) {
+        let mut buf = BytesMut::with_capacity(16/8);
+        buf.put_u16_be(*self);
+        s.extend_buffer(&mut buf.to_vec());
+    }
+}
 
 impl Encodable for u32 {
     fn ssz_append(&self, s: &mut SszStream) {
         let mut buf = BytesMut::with_capacity(32/8);
         buf.put_u32_be(*self);
-        s.append_encoded_vec(&mut buf.to_vec());
+        s.extend_buffer(&mut buf.to_vec());
     }
 }
 
@@ -88,13 +107,13 @@ impl Encodable for u64 {
     fn ssz_append(&self, s: &mut SszStream) {
         let mut buf = BytesMut::with_capacity(64/8);
         buf.put_u64_be(*self);
-        s.append_encoded_vec(&mut buf.to_vec());
+        s.extend_buffer(&mut buf.to_vec());
     }
 }
 
 impl Encodable for H256 {
     fn ssz_append(&self, s: &mut SszStream) {
-        s.append_encoded_vec(&mut self.to_vec());
+        s.extend_buffer(&mut self.to_vec());
     }
 }
 
@@ -110,7 +129,7 @@ impl Encodable for U256 {
 #[cfg(test)]
 mod tests {
     use super::*;
-    
+
     #[test]
     #[should_panic]
     fn test_encode_length_0_bytes_panic() {
@@ -140,7 +159,7 @@ mod tests {
             vec![255, 255, 255, 255]
         );
     }
-    
+
     #[test]
     #[should_panic]
     fn test_encode_length_4_bytes_panic() {
@@ -152,7 +171,7 @@ mod tests {
         pub struct TestStruct {
             pub one: u32,
             pub two: H256,
-            pub three: u64,        
+            pub three: u64,
         }
 
         impl Encodable for TestStruct {