This is an exhaust gasket set for the OS 10LA and 15LA engines. These gaskets are installed between the crankcase and a 871 muffler. INCLUDES: Three Exhaust Gaskets REQUIRES: Installation onto engine SPECS: Length: 34mm (1.33") C.D. between mounting holes: 28.5mm (1.12") COMMENTS: These gaskets are made specifically for a 871 silencer. cmc 11/29/01 ir/kh