Thunder Shift TRA arms for the Ski-doo TRA 3 clutches allow weight to be placed at different locations on the arm. This helps tune the shift and belt squeeze more precisely than stock arms. We stock part # TSA-395 which is the medium weight and works well in all 600cc and up applications we have tested. Any stock or aftermarket pin kits work with these arms. We also have tuning data to help you get "in the ballpark" for your application.