REFINED & IMPROVED FOR 2017 - We have refined our Summit kit which resulted in increased track speed and even faster backshift for 2017. Several 872- 3"test sleds have gone from 45-47 mph stock track speed to 59-62 mph big bore track speed with our refined 2017 kit. The Hot Rod Sled Shop Clutch Kit for Ski-doo Summit Models from various 860, Trygstad 872, and various 880 Big Bore 146-174" sleds has been tested on various 860R to 880R Summit models from 1.75 to 3" tracks and altitudes from sea-level to 12k. The words out, we have a kit that holds rpm, pulls like a freight train, backshifts lightening quick, creates less sheave heat, and allows perfect throttle to track control. This is also a dual elevation kit with pinweight change only from sea-level to 12k. Again our kits are built to engage soft without trenching around at 3500 rpm . The clutch sheaves run noticeably cooler than a stock setup with just pinweight added. The kit includes HRSS1 ramps, Helix, Hot Rod Sled Shop Adjustable light or medium pin kit, primary spring, and secondary spring and we have added our QRS SlickShift Bearing also. Our Kit works really well with stock TRA arms and the oem QRS secondary clutch, but we have very accurate data for guys using Toms 3D Arms or Thundershift Arms with our primary components. We also have very good base data with our kit if you are using the TEAM TSS-04 or TEAM Tied secondary clutch, and can offer you primary components and helix for that application.