Universal brass instrument valve stem thick cork washers, each purchase gets one set of 3, you choose your size. 

Fits stems for 20J. 20K, tubas and sousaphones.  See my item ID# 275133568893 for a smaller variety of cork washers.  For red felts, see my item ID# 275672696770 (those with a 7/32 ID will work on a Conn 20K Sousaphone stem).