diff --git a/Data/Repa/Scalar/Box.hs b/Data/Repa/Scalar/Box.hs
--- a/Data/Repa/Scalar/Box.hs
+++ b/Data/Repa/Scalar/Box.hs
@@ -1,6 +1,7 @@
 
 module Data.Repa.Scalar.Box
-        ( Box           (..))
+        ( Box           (..)
+        , box, unbox)
 where
 import qualified Data.Vector                    as V
 import qualified Data.Vector.Unboxed            as U
@@ -8,6 +9,7 @@
 import qualified Data.Vector.Generic.Mutable    as GM
 
 
+
 -- | Strict, boxed wrapper for a value.
 --
 --   Useful as a default case when defining instances for polytypic 
@@ -17,6 +19,23 @@
         deriving (Eq, Show)
 
 
+-- | Put a value in a box.
+box   :: a -> Box a
+box !x = Box x
+{-# INLINE box #-}
+
+
+-- | Take the value from the box.
+unbox :: Box a -> a
+unbox (Box x) = x
+{-# INLINE unbox #-}
+
+
+instance Functor Box where
+ fmap f (Box x) = Box (f x)
+ {-# INLINE fmap #-}
+
+
 -- Unboxed ----------------------------------------------------------------------------------------
 -- Unboxed instance adapted from:
 -- http://code.haskell.org/vector/internal/unbox-tuple-instances
@@ -33,8 +52,7 @@
         !(V.MVector s a)
 
 
-instance U.Unbox a
-      => GM.MVector U.MVector (Box a) where
+instance GM.MVector U.MVector (Box a) where
 
   basicLength (MV_Box n _as) = n
   {-# INLINE basicLength  #-}
@@ -88,8 +106,7 @@
   {-# INLINE basicUnsafeGrow  #-}
 
 
-instance U.Unbox a
-      => G.Vector U.Vector (Box a) where
+instance G.Vector U.Vector (Box a) where
 
   basicUnsafeFreeze (MV_Box n as)
    = do as' <- G.basicUnsafeFreeze as
diff --git a/Data/Repa/Scalar/Option.hs b/Data/Repa/Scalar/Option.hs
--- a/Data/Repa/Scalar/Option.hs
+++ b/Data/Repa/Scalar/Option.hs
@@ -44,6 +44,12 @@
 {-# INLINE fromOption #-}
 
 
+instance Functor Option where
+ fmap _ None     = None
+ fmap f (Some x) = Some (f x)
+ {-# INLINE fmap #-}
+
+
 -------------------------------------------------------------------------------
 -- | A strict `Maybe` type, with two parameters.
 data Option2 a b
@@ -66,6 +72,12 @@
 {-# INLINE fromOption2 #-}
 
 
+instance Functor (Option2 a) where
+ fmap _ None2       = None2
+ fmap f (Some2 x y) = Some2 x (f y)
+ {-# INLINE fmap #-}
+
+
 -------------------------------------------------------------------------------
 -- | A strict `Maybe` type with three parameters.
 data Option3 a b c
@@ -88,6 +100,12 @@
 {-# INLINE fromOption3 #-}
 
 
+instance Functor (Option3 a b) where
+ fmap _ None3         = None3
+ fmap f (Some3 x y z) = Some3 x y (f z)
+ {-# INLINE fmap #-}
+
+
 -------------------------------------------------------------------------------
 -- | A strict `Maybe` type with four parameters.
 data Option4 a b c d
@@ -108,4 +126,10 @@
 fromOption4 None4                 = Nothing
 fromOption4 (Some4 x1 x2 x3 x4)   = Just (x1, x2, x3, x4)
 {-# INLINE fromOption4 #-}
+
+
+instance Functor (Option4 a b c) where
+ fmap _ None4           = None4
+ fmap f (Some4 x y z a) = Some4 x y z (f a)
+ {-# INLINE fmap #-}
 
diff --git a/Data/Repa/Scalar/Product.hs b/Data/Repa/Scalar/Product.hs
--- a/Data/Repa/Scalar/Product.hs
+++ b/Data/Repa/Scalar/Product.hs
@@ -30,6 +30,9 @@
 
 infixr :*:
 
+instance Functor ((:*:) a) where
+ fmap f ((:*:) x y) = (:*:) x (f y)
+
 
 -- | Sequences of products that form a valid list, 
 --   using () for the nil value.
diff --git a/repa-scalar.cabal b/repa-scalar.cabal
--- a/repa-scalar.cabal
+++ b/repa-scalar.cabal
@@ -1,5 +1,5 @@
 Name:           repa-scalar
-Version:        4.2.1.1
+Version:        4.2.2.1
 License:        BSD3
 License-file:   LICENSE
 Author:         The Repa Development Team