King 3rd Valve Stopper Screw, P/N BG13041NP for King 1121 marching mellophone & 1129 marching euphoniums. P/N BG13042NP for 1117 & SB12 marching trumpet. See my item ID# 16694 or 28109 for Stradivarius trumpets. Contact me if you wish to verify your model's fit or you need parts for another horn.
