diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,4 +1,8 @@
 # Changelog for depq
 
+## 0.3
+* Add 'size'
+* Add dependency lower bounds
+
 ## 0.1
 First release
diff --git a/depq.cabal b/depq.cabal
--- a/depq.cabal
+++ b/depq.cabal
@@ -1,5 +1,5 @@
 name:           depq
-version:        0.2.0.0
+version:        0.3.0.0
 synopsis:       Double-ended priority queues
 description:    Double-ended priority queues, for efficient retrieval of minimum and maximum elements in ordered collections of items.
 homepage:       https://github.com/ocramz/depq
diff --git a/src/Data/DEPQ.hs b/src/Data/DEPQ.hs
--- a/src/Data/DEPQ.hs
+++ b/src/Data/DEPQ.hs
@@ -7,11 +7,13 @@
 Based on `P.IntPSQ` : https://hackage.haskell.org/package/psqueues-0.2.7.2/docs/Data-IntPSQ.html
 -}
 module Data.DEPQ (
-   DEPQ,
+   DEPQ, 
    -- * Creation
    empty, fromList,
    -- * Predicates
    null,
+   -- * Properties
+   size, 
    -- * Modification
    insert, deleteMin, deleteMax, popMin, popMax,
    -- * Lookup
@@ -28,7 +30,7 @@
 -- deepseq
 import Control.DeepSeq     (NFData (rnf))
 -- psqueues
-import qualified Data.IntPSQ as P (IntPSQ, empty, null, insert, delete, member, toList, fromList, findMin, delete, deleteMin)
+import qualified Data.IntPSQ as P (IntPSQ, empty, null, size, insert, delete, member, toList, fromList, findMin, delete, deleteMin)
 
 import Prelude hiding (null)
 
@@ -61,6 +63,10 @@
 empty :: DEPQ p a
 empty = DEPQ P.empty P.empty
 
+-- | Number of elements in the DEPQ
+size :: DEPQ p a -> Int
+size (DEPQ p _) = P.size p
+
 -- | Populate a DEPQ from a 'Foldable' container (e.g. a list)
 fromList :: (Foldable t, Ord p) =>
             t (Int, p, a) -- ^ (key, priority, value)
@@ -120,10 +126,14 @@
   pure (x, q')
 
 -- | K highest-scoring entries in the DEPQ
+--
+-- NB : this returns an empty sequence if there are fewer than K elements in the DEPQ
 topK :: Ord p => Int -> DEPQ p v -> S.Seq (Int, p, v)
 topK = popK popMax
 
 -- | K lowest-scoring entries in the DEPQ
+--
+-- NB : this returns an empty sequence if there are fewer than K elements in the DEPQ
 bottomK :: Ord p => Int -> DEPQ p v -> S.Seq (Int, p, v)
 bottomK = popK popMin