Yamaha OEM Baritone YBH-301 & others. 3 or 4 G2141093 guides.  Approximately 18mm x 13mm with metal insert.  For the larger valve guides for Sousaphones & Tubas, see my item ID# .Fits:YBH-100SYBH-201YBH-301YBH-301(2)YBH-301MYBH-301MSYBH-301SYBH-301S(2)YBH-621YBH-621(2)YBH-621SYBH-621S(2)YBH-831YBH-831SYEP-202MYEP-202MSYamaha OEM YBH-621, 4 Valve, Baritone Valve Guide Set of 4. Fits:YBH-621YBH-621(2)YBH-621SYBH-621S(2)