diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,9 @@
 # Revision history for network-control
 
+## 0.0.2
+
+* Adding constants.
+
 ## 0.0.1
 
 * Supporting GHC 8.10.
diff --git a/Network/Control/Flow.hs b/Network/Control/Flow.hs
--- a/Network/Control/Flow.hs
+++ b/Network/Control/Flow.hs
@@ -1,6 +1,11 @@
 {-# LANGUAGE RecordWildCards #-}
 
 module Network.Control.Flow (
+    -- * Constants for flow control.
+    defaultMaxStreams,
+    defaultMaxStreamData,
+    defaultMaxData,
+
     -- * Flow control for sending
     TxFlow (..),
     newTxFlow,
@@ -16,6 +21,18 @@
 ) where
 
 import Data.Bits
+
+-- | Default max streams. (64)
+defaultMaxStreams :: Int
+defaultMaxStreams = 64
+
+-- | Default max data of a stream. (256K bytes)
+defaultMaxStreamData :: Int
+defaultMaxStreamData = 262144
+
+-- | Default max data of a connection. (1M bytes)
+defaultMaxData :: Int
+defaultMaxData = 1048576
 
 -- | Window size.
 type WindowSize = Int
diff --git a/network-control.cabal b/network-control.cabal
--- a/network-control.cabal
+++ b/network-control.cabal
@@ -1,6 +1,6 @@
 cabal-version:   3.0
 name:            network-control
-version:         0.0.1
+version:         0.0.2
 license:         BSD-3-Clause
 license-file:    LICENSE
 maintainer:      kazu@iij.ad.jp