Oregon 38470X 3/8" Pitch 7-Tooth Standard 7 Spline Power Mate Rim Sprocket System Oregon 38470X Replacement Power Mate Sprocket System includes a drum with a replaceable rim, allowing the rim to be replaced.(Bearing 37504 sold separately) For 3/8" Pitch Chain Saws, 7-Tooth Sprocket, Standard 7 Spline (Sd7) Rim Sprocket System Replacement schedule: Every three rims For use on Stihl 044, 046, MS 361, MS 362, MS440, MS 460 Rim sprocket systems are favored by those who want the ultimate in performance and durability