diff --git a/library/STMContainers/Bimap.hs b/library/STMContainers/Bimap.hs
--- a/library/STMContainers/Bimap.hs
+++ b/library/STMContainers/Bimap.hs
@@ -2,6 +2,7 @@
 (
   Bimap,
   Association,
+  Key,
   new,
   newIO,
   insert1,
@@ -30,10 +31,15 @@
 -- of the right-hand type and vice versa.
 data Bimap a b = 
   Bimap {m1 :: !(Map.Map a b), m2 :: !(Map.Map b a)}
+  deriving (Typeable)
 
 -- |
--- A standard constraint for associations.
-type Association a b = (Map.Key a, Map.Key b)
+-- A constraint for associations.
+type Association a b = (Key a, Key b)
+
+-- |
+-- A constraint for keys.
+type Key k = Map.Key k
 
 -- |
 -- Construct a new bimap.
diff --git a/library/STMContainers/Map.hs b/library/STMContainers/Map.hs
--- a/library/STMContainers/Map.hs
+++ b/library/STMContainers/Map.hs
@@ -21,22 +21,19 @@
 
 -- |
 -- A hash table, based on an STM-specialized hash array mapped trie.
-newtype Map k v = Map (HAMT.HAMT (Association k v))
+newtype Map k v = Map (HAMT.HAMT (k, v))
+  deriving (Typeable)
 
 -- |
--- A standard constraint for keys.
+-- A constraint for keys.
 type Key a = (Eq a, Hashable a)
 
--- |
--- A key-value association.
-type Association k v = (k, v)
-
-instance (Eq k) => HAMTNodes.Element (Association k v) where
-  type ElementKey (Association k v) = k
+instance (Eq k) => HAMTNodes.Element (k, v) where
+  type ElementKey (k, v) = k
   elementKey (k, v) = k
 
 {-# INLINE associationValue #-}
-associationValue :: Association k v -> v
+associationValue :: (k, v) -> v
 associationValue (_, v) = v
 
 -- |
diff --git a/library/STMContainers/Multimap.hs b/library/STMContainers/Multimap.hs
--- a/library/STMContainers/Multimap.hs
+++ b/library/STMContainers/Multimap.hs
@@ -2,6 +2,8 @@
 (
   Multimap,
   Association,
+  Key,
+  Value,
   new,
   newIO,
   insert,
@@ -25,10 +27,19 @@
 -- 
 -- Basically it's just a wrapper API around @'Map.Map' k ('Set.Set' v)@.
 newtype Multimap k v = Multimap (Map.Map k (Set.Set v))
+  deriving (Typeable)
 
 -- |
--- A standard constraint for items.
-type Association k v = (Eq k, Hashable k, Eq v, Hashable v)
+-- A constraint for associations.
+type Association k v = (Key k, Value v)
+
+-- |
+-- A constraint for keys.
+type Key k = Map.Key k
+
+-- |
+-- A constraint for values.
+type Value v = Set.Element v
 
 -- |
 -- Look up an item by a value and a key.
diff --git a/library/STMContainers/Set.hs b/library/STMContainers/Set.hs
--- a/library/STMContainers/Set.hs
+++ b/library/STMContainers/Set.hs
@@ -22,9 +22,10 @@
 -- |
 -- A hash set, based on an STM-specialized hash array mapped trie.
 newtype Set e = Set {hamt :: HAMT.HAMT (HAMTElement e)}
+  deriving (Typeable)
 
 -- |
--- A standard constraint for elements.
+-- A constraint for elements.
 type Element a = (Eq a, Hashable a)
 
 newtype HAMTElement e = HAMTElement e
diff --git a/stm-containers.cabal b/stm-containers.cabal
--- a/stm-containers.cabal
+++ b/stm-containers.cabal
@@ -1,7 +1,7 @@
 name:
   stm-containers
 version:
-  0.2.4
+  0.2.5
 synopsis:
   Containers for STM
 description: