diff --git a/src/block.rs b/src/block.rs
index b15d512..1ef01cb 100644
--- a/src/block.rs
+++ b/src/block.rs
@@ -22,29 +22,67 @@ pub trait BitBlock
     const ZERO: Self;
     const ONE: Self;
 
-    fn bits() -> u8;
+    fn bits() -> usize;
     fn count_ones(self) -> usize;
+
+    fn block(value: Self) -> Self;
+    fn bit(value: Self) -> Self;
 }
 
-macro_rules! bit_block_impl {
+pub trait Block
+    : Copy
+    + Hash
+    + Eq
+    + Shl<Self, Output = Self>
+    + BitAnd<Self, Output = Self>
+    + BitOr<Self, Output = Self>
+    + Not<Output = Self> {
+    const ZERO: Self;
+    const ONE: Self;
+
+    fn bits() -> usize;
+    fn count_ones(self) -> usize;
+
+    fn block<B>(value: Self) -> Self
+    where
+        B: Block;
+    fn bit<B>(value: B) -> Self
+    where
+        B: Block;
+
+    fn biter<B>(value: Self) -> u8
+    where
+        B: Block;
+}
+
+macro_rules! block_impl {
     ($(($t: ty, $size: expr)),*) => ($(
-        impl BitBlock for $t {
+        impl Block for $t {
             const ZERO: Self = 0;
             const ONE: Self = 1;
 
             #[inline]
-            fn bits() -> u8 { $size }
+            fn bits() -> usize { $size }
 
             #[inline]
             fn count_ones(self) -> usize { self.count_ones() as usize }
+
+            #[inline]
+            fn block<B>(value: Self) -> Self where B: Block { value / B::bits() as Self }
+
+            #[inline]
+            fn bit<B>(value: B) -> Self where B: Block { B::biter::<Self>(value) as Self }
+
+            #[inline]
+            fn biter<B>(value: Self) -> u8 where B: Block { (value % B::bits() as Self) as u8 }
         }
     )*)
 }
 
-bit_block_impl!{
+block_impl!{
     (u8, 8),
     (u16, 16),
     (u32, 32),
     (u64, 64),
-    (usize, (mem::size_of::<usize>() * 8) as u8)
+    (usize, mem::size_of::<usize>() * 8)
 }
diff --git a/src/lib.rs b/src/lib.rs
index a8d27de..ea95ed5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,29 +15,29 @@ mod hasher;
 mod block;
 
 use hasher::BitBuildHasher;
-use block::BitBlock;
+use block::Block;
 
 pub type BitHashMap<V> = HashMap<u64, V, BitBuildHasher>;
 
 #[inline]
-fn get_block_and_bit<T, B>(x: T) -> (T, B)
+fn index<T, B>(value: T) -> (T, B)
 where
-    T: BitBlock,
-    B: BitBlock,
+    T: Block,
+    B: Block,
 {
-    (x / T::from(B::bits()), x % T::from(B::bits())
+    (T::block::<B>(value), B::bit(value))
 }
 
 #[derive(PartialEq)]
-pub struct BitSet<T: BitBlock, B: BitBlock = u64> {
+pub struct BitSet<T: Block, B: Block = u64> {
     blocks: HashMap<T, B, BitBuildHasher>,
     nbits: usize,
 }
 
 impl<T, B> BitSet<T, B>
 where
-    T: BitBlock,
-    B: BitBlock,
+    T: Block,
+    B: Block,
 {
     #[inline]
     pub fn new() -> BitSet<T, B> {
@@ -50,7 +50,10 @@ where
     #[inline]
     pub fn with_capacity(capacity: usize) -> BitSet<B> {
         BitSet {
-            blocks: HashMap::with_capacity_and_hasher(capacity / B::bits() as usize, Default::default()),
+            blocks: HashMap::with_capacity_and_hasher(
+                capacity / B::bits() as usize,
+                Default::default(),
+            ),
             nbits: 0,
         }
     }
@@ -94,40 +97,40 @@ where
     }
 
     pub fn contains(&self, value: &T) -> bool {
-        let (block, bit) = get_block_and_bit::<T, B>(*value);
+        let (block, bit) = index::<T, B>(*value);
 
         match self.blocks.get(&block) {
-            Some(block) => (block & (B::ONE << bit)) != B::ZERO,
+            Some(block) => (*block & (B::ONE << bit)) != B::ZERO,
             None => false,
         }
     }
-    /*
-    pub fn is_subset(&self, other: &BitSet<B>) -> bool {
+
+    pub fn is_subset(&self, other: &BitSet<T, B>) -> bool {
         if self.nbits > other.nbits {
             false
         } else {
             self.blocks
                 .iter()
                 .all(|(key, block_a)| match other.blocks.get(key) {
-                    Some(block_b) => block_a | block_b == *block_b,
-                    None => *block_a == 0,
+                    Some(block_b) => *block_a | *block_b == *block_b,
+                    None => *block_a == B::ZERO,
                 })
         }
     }
 
     #[inline]
-    pub fn is_superset(&self, other: &BitSet<B>) -> bool {
+    pub fn is_superset(&self, other: &BitSet<T, B>) -> bool {
         other.is_subset(self)
     }
 
-    pub fn insert(&mut self, value: u64) -> bool {
-        let (block, bit) = get_block_and_bit::<B>(&value);
-        let block = self.blocks.entry(block).or_insert(0);
+    pub fn insert(&mut self, value: T) -> bool {
+        let (block, bit) = index::<T, B>(value);
+        let block = self.blocks.entry(block).or_insert(B::ZERO);
 
-        let n = 1 << bit;
+        let n = B::ONE << bit;
 
-        if (*block & n) == 0 {
-            *block |= n;
+        if (*block & n) == B::ZERO {
+            *block = *block | n;
             self.nbits += 1;
 
             true
@@ -136,14 +139,14 @@ where
         }
     }
 
-    pub fn remove(&mut self, value: &u64) -> bool {
-        let (block, bit) = get_block_and_bit::<B>(value);
-        let block = self.blocks.entry(block).or_insert(0);
+    pub fn remove(&mut self, value: &T) -> bool {
+        let (block, bit) = index::<T, B>(*value);
+        let block = self.blocks.entry(block).or_insert(B::ZERO);
 
-        let n = 1 << bit;
+        let n = B::ONE << bit;
 
-        if (*block & n) != 0 {
-            *block &= !n;
+        if (*block & n) != B::ZERO {
+            *block = *block & !n;
             self.nbits -= 1;
 
             true
@@ -154,93 +157,97 @@ where
 
     pub fn union_with(&mut self, other: &Self) {
         for (key, value) in &other.blocks {
-            *self.blocks.entry(*key).or_insert(0) |= value;
+            let block = self.blocks.entry(*key).or_insert(B::ZERO);
+            *block = *block | *value;
         }
 
         self.nbits = self.blocks
             .values()
-            .map(|block| block.count_ones() as usize)
+            .map(|block| B::count_ones(*block))
             .sum();
     }
-    */
 }
+
 /*
-impl<B> fmt::Debug for BitSet<B> {
+impl<T, B> fmt::Debug for BitSet<T, B> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_set().entries(self.iter()).finish()
     }
 }
+*/
 
-impl<B> FromIterator<u64> for BitSet<B> {
+impl<T, B> FromIterator<T> for BitSet<T, B> where T: Block, B: Block {
     #[inline]
-    fn from_iter<I: IntoIterator<Item = u64>>(iter: I) -> BitSet<B> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BitSet<T, B> {
         let mut set = BitSet::new();
         set.extend(iter);
         set
     }
 }
 
-impl<B> Extend<u64> for BitSet<B> {
+impl<T, B> Extend<T> for BitSet<T, B> where T: Block, B: Block {
     #[inline]
-    fn extend<I: IntoIterator<Item = u64>>(&mut self, iter: I) {
+    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
         for i in iter {
             self.insert(i);
         }
     }
 }
 
-impl<'a, B> Extend<&'a u64> for BitSet<B> {
+impl<'a, T: 'a, B> Extend<&'a T> for BitSet<T, B> where T: Block, B: Block {
     #[inline]
-    fn extend<I: IntoIterator<Item = &'a u64>>(&mut self, iter: I) {
+    fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
         for i in iter {
             self.insert(*i);
         }
     }
 }
 
-impl<B> Default for BitSet<B> {
+impl<T, B> Default for BitSet<T, B> where T: Block, B: Block {
     #[inline]
-    fn default() -> BitSet<B> {
+    fn default() -> BitSet<T, B> {
         BitSet::new()
     }
 }
 
-impl<B> ops::BitOr for BitSet<B> {
+impl<T, B> ops::BitOr for BitSet<T, B> where T: Block, B: Block {
     type Output = Self;
 
     #[inline]
     fn bitor(mut self, rhs: Self) -> Self {
         for (key, value) in &rhs.blocks {
-            *self.blocks.entry(*key).or_insert(0) |= value;
+            let block = self.blocks.entry(*key).or_insert(B::ZERO);
+            *block = *block | *value;
         }
 
         self.nbits = self.blocks
             .values()
-            .map(|block| block.count_ones() as usize)
+            .map(|block| block.count_ones())
             .sum();
 
         self
     }
 }
 
-impl<'a, B> ops::BitOr<&'a Self> for BitSet<B> {
+impl<'a, T, B> ops::BitOr<&'a Self> for BitSet<T, B> where T: Block, B: Block {
     type Output = Self;
 
     #[inline]
     fn bitor(mut self, rhs: &'a Self) -> Self {
         for (key, value) in &rhs.blocks {
-            *self.blocks.entry(*key).or_insert(0) |= value;
+            let block = self.blocks.entry(*key).or_insert(B::ZERO);
+            *block = *block | *value;
         }
 
         self.nbits = self.blocks
             .values()
-            .map(|block| block.count_ones() as usize)
+            .map(|block| block.count_ones())
             .sum();
 
         self
     }
 }
-
+/*
 pub struct Iter<'a> {
     iter: std::collections::hash_map::Iter<'a, u64, u64>,
     block: u64,