This is a A-B1RS5156 Timber Ridge 3/8" Drive Sprocket PN: B1RS5156Main Description As Following : A-B1RS5156 Timber Ridge 3/8" Drive Sprocket P.N: B1RS5156 Crankshaft: 0.5Pitch: 3/8Teeth: 7Type: Rim System Replaces: B15156 TIMBER RIDGE , Crossed From: 26831 OREGON Found in Section & Models : Sunbelt - Chainsaw & Forestry > Sprockets, Timber Ridge CHAINSAW CLUTCH DRUM RIM: SEVERAL Associated Items : New Also This is An Aftermarket Product And : Crankshaft: 0.5 Pitch: 3/8 Teeth: 7 Type: Rim System