diff --git a/Data/BoundingBox.hs b/Data/BoundingBox.hs
--- a/Data/BoundingBox.hs
+++ b/Data/BoundingBox.hs
@@ -20,6 +20,7 @@
 import Data.Traversable as Traversable
 
 -- | The type of bounding box for arbitrary vector @f@.
+-- The functions for this type assume that @f@ is a "zipping" 'Applicative'.
 data Box f a = Box (f a) (f a) deriving (Show, Eq, Ord, Functor, Foldable, Traversable, Read)
 
 instance Applicative f => Applicative (Box f) where
diff --git a/boundingboxes.cabal b/boundingboxes.cabal
--- a/boundingboxes.cabal
+++ b/boundingboxes.cabal
@@ -1,13 +1,13 @@
 name:                boundingboxes
-version:             0.2
-synopsis:            The type for 2D bounding box
+version:             0.2.1
+synopsis:            A generic boundingbox for an arbitrary vector
 -- description:         
 homepage:            https://github.com/fumieval/boundingboxes
 license:             BSD3
 license-file:        LICENSE
 author:              Fumiaki Kinoshita
 maintainer:          fumiexcel@gmail.com
--- copyright:           
+copyright:           Copyright (c) 2014 Fumiaki Kinoshita
 category:            Data
 build-type:          Simple
 -- extra-source-files:  
diff --git a/tests/properties.hs b/tests/properties.hs
--- a/tests/properties.hs
+++ b/tests/properties.hs
@@ -27,7 +27,7 @@
 prop_resize bb (getReference -> ref) sz = nearZero $ bb ^. position ref - bb' ^. position ref where
     bb' = bb & size ref .~ getPositive sz :: Box V2 Float
 
-prop_rearrange (getReference -> ref) bb pos = nearZero $ bb ^. size 0 - bb' ^. size 0 where
+prop_rearrange (getReference -> ref) bb pos = norm (bb ^. size 0 - bb' ^. size 0) < 10e-4 where
     bb' = bb & position ref .~ pos :: Box V2 Float
 
 prop_construct (getReference -> ref) pos (getPositive -> sz) = nearZero (bb ^. size 0 - sz)