diff --git a/README.md b/README.md
index ac429ead..e68788f0 100644
--- a/README.md
+++ b/README.md
@@ -328,6 +328,13 @@ Error handling:
 Constraints:
 
 - Clonable
+- BePrinter
+- BePrintfer
+- BeWriter
+- BeReader
+- BeCloser
+- BeSeeker
+- BeReadWriter
 
 ### Filter