diff --git a/ffi/cs/readme.md b/ffi/cs/readme.md
index e5f2785..a9872a7 100644
--- a/ffi/cs/readme.md
+++ b/ffi/cs/readme.md
@@ -9,3 +9,7 @@ mklib dll
 ```
 
 Open `ffi/cs/mcl.sln` and Set the directory of `mcl/bin` to `workingDirectory` at `Debug` of test project.
+
+# Remark
+- `bn256.cs` is an old code. It will be removed in the future.
+- `mcl/mcl.cs` is a new version. It support `BN254`, `BN_SNARK` and `BLS12_381` curve, which requires `mclbn384_256.dll`.
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