Oregon 34162X 3/8" Pitch 7-Tooth Small 7 Spline Power Mate Rim Sprocket System Oregon 34162X Replacement Power Mate Sprocket System includes a drum with a replaceable rim, allowing the rim to be replaced.(Bearing 37325 sold separately) For 3/8" Pitch Chain Saws, 7-Tooth Sprocket, Small 7 Spline (Sm7) Rim Sprocket System Replacement schedule: Every three rims For use on Stihl 029, 034, 024 Super, 036, 039, MS 290, MS 360, MS 390 Saws Rim sprocket systems are favored by those who want the ultimate in performance and durability