The thunder shift kit differs from all other clutch kits or components by offering adjustable weight in increments of .2 to .4 grams at a time. TSK components are made of the highest quality available. There are 2 kits available for the Ski Doo TRA clutches. TSK-190 has extra light roller pins and covers a weight range of 3.7 to 18.0 grams. TSK-195 has steel roller pins and covers a weight range of 10.1 to 24.4 grams. There is an optional heavy duty kit which includes 6 Tungsten washer weights. They are 3.4 grams each which could make maximum weight to 30 grams. Thunder shift arms fit TRA II & TRA III clutches. Fully adjustable in low and mid range for quicker acceleration and faster backshift. Find the perfect shift curve with adjustment resolutions as fine as .4 gram. Use with Thunder Shift Arms for unlimited tuning options. We also have the Thunder Shift Arms for the TRA & TRAIII. The shift arms allow for quicker acceleration and faster backshift. They are fully adjustable in low and mid range. They offer an optional threaded pin which allows for top end tuning. You can find the perfect shift curve with adjustment resolutions as fine as .4 gram. Use the shift arms with the Thunder Shift kit for unlimited tuning options.