See my item # 16196 for a YEP-201/201M and 16029 for a YEP-202M and YBH-301M Marching Baritone and Euphonium Repair Kit. They are different kits.
4 valve, Euphonium YEP-321 & YEP-621 Valve Repair Kit (after 1986). 4 each guides, springs, valve stem felts & pads, top cap felts & pads, stem washers (metal), and 2 each water key corks.
4 valve, Euphonium YEP-321 & YEP-621 springs and felts kit (before 1986). 4 each springs, valve stem and top cap felts.
4 valve YEP-642 & YEP-842 Euphonium; 4 each guides, springs, valve stem pads, button pads, stem washers (metal), 3 cork stem washers for valves 1, 2, & 3, and 2 each water key corks.
Contact me with your model if you wish to verify your model's fit.