DOP100961XST Power Mate Rim/Sprocket System .325" Pitch-7 Tooth fits Stihl Chain saws. Clutch drum with rim. Does not include bearing, must order Bearing # 37325 separately. Fits Stihl model 017, 018, 018 C, 019, 021, 023, 023 C, 025, MS 210, MS 250, MS 250 C Chainsaws.