diff --git a/Control/Lens.hs b/Control/Lens.hs
--- a/Control/Lens.hs
+++ b/Control/Lens.hs
@@ -1,4 +1,4 @@
-module Control.Lens (Lens, Refractor, Traversal, Iso,
+module Control.Lens (Lens, Traversal, Iso,
                      lens, iso,
                      get, set, modify, mapping,
                      fstL, sndL, swapL, unitL, bitL) where
@@ -6,7 +6,6 @@
 import Prelude hiding (id)
 
 import Control.Applicative
-import Control.Arrow
 import Control.Category
 import Control.Category.Unicode
 import Data.Bits (Bits (..))
@@ -15,13 +14,11 @@
 import Data.Profunctor
 import Data.Tuple (swap)
 
-type Refractor c d α β a b = ∀ p f . (d f, c p) ⇒ p a (f b) → p α (f β)
-
-type Lens α β a b = Refractor ((~) (→)) Functor α β a b
+type Lens α β a b = ∀ f . Functor f => (a -> f b) -> (α -> f β)
 
-type Traversal α β a b = Refractor ((~) (→)) Applicative α β a b
+type Traversal α β a b = ∀ f . Applicative f => (a -> f b) -> (α -> f β)
 
-type Iso α β a b = Refractor Profunctor Functor α β a b
+type Iso α β a b = ∀ p f . (Profunctor p, Functor f) ⇒ p a (f b) -> p α (f β)
 
 lens :: (α → a) → (b → α → β) → Lens α β a b
 lens get set ret = liftA2 fmap (flip set) (ret ∘ get)
@@ -42,13 +39,13 @@
 mapping = (`withIso` \ f g -> iso (fmap f) (fmap g))
 
 withIso :: AnIso α β a b -> ((α -> a) -> (b -> β) -> c) -> c
-withIso x = case x (Xchg id Identity) of Xchg φ φ' -> \ f -> f φ (runIdentity ∘ φ')
+withIso x = case x (Xchg id Identity) of Xchg φ χ -> \ f -> f φ (runIdentity ∘ χ)
 
 type AnIso α β a b = Xchg a b a (Identity b) -> Xchg a b α (Identity β)
 
 data Xchg a b α β = Xchg (α -> a) (b -> β) deriving (Functor)
 
-instance Profunctor (Xchg a b) where dimap f g (Xchg φ φ') = Xchg (φ ∘ f) (g ∘ φ')
+instance Profunctor (Xchg a b) where dimap f g (Xchg φ χ) = Xchg (φ ∘ f) (g ∘ χ)
 
 fstL :: Lens (a, c) (b, c) a b
 fstL = swapL ∘ sndL
diff --git a/lenz.cabal b/lenz.cabal
--- a/lenz.cabal
+++ b/lenz.cabal
@@ -1,5 +1,5 @@
 name:           lenz
-version:        0.2.2.1
+version:        0.3.0.0
 synopsis:       Van Laarhoven lenses
 license:        BSD3
 author:	        M Farkas-Dyck
@@ -16,7 +16,7 @@
   exposed-modules:      Control.Lens
   build-depends:        base >= 4.8 && <5
                       , base-unicode-symbols >= 0.1 && <0.3
-                      , hs-functors >=0.1 && <0.2
+                      , hs-functors >=0.1.1 && <0.2
                       , transformers >=0.2 && <0.6
-  extensions:           UnicodeSyntax, RankNTypes, ConstraintKinds, GADTs, DeriveFunctor
+  extensions:           UnicodeSyntax, RankNTypes, ConstraintKinds, DeriveFunctor
   ghc-options:          -Wall -Wno-name-shadowing