HOT ROD SLED SHOP INC SKI-DOO REV GEN4 600R ETEC CLUTCH KIT: ThIs kit includes our chromemoly heat-treated electroless nickel plated HRSS-PDL clutch ramps, HRSS H5 primary Pdrive spring, HRSS H5 QRS secondary spring and a progressive cut helix. We have calibrations for 129-137 sleds and a 146 backcountry calibration as well. The result is hard acceleration, superior backshift and much quicker throttle response to the track in on/off corner -to- corner trail riding. It's a much more responsive ride that takes advantage of this awesome motor/chassis package from Ski-doo. Belt temps are significantly reduced from the oem clutch calibration. Our friends at Grip-N-RIP Racing have reported 30 degree less sheave heat and far superior performance with this kit. This is the same kit used by IRON DOG Team 6 who switched to this kit for better top speed & belt longevity. Our HRSS-PDL2 weights eliminate the stock "clicker" system for our weight which controls shift via magnets added or subtracted for the 4 hole positions in the ramp. It's a simple superior design with far better backshift and upshift profile that we took two years to design and perfect. Tested with 4 mile wide open pulls and very acceptable clutch heat. The backcountry calibration holds rpm in the deep and pulls really hard on the trail (oem clutching is an rpm fluctuating mess on this model). Kits come with complete instruction sheet and calibrations for your application.