This shim kit moves the QRS secondary clutch out 3mm for proper belt alignment and gets 99% of the ski-doo's in alignment. That black belt residue all over your secondary clutch and cover is from the misalignment of the factory clutches. This spacer kit has a 3mm shim to put behind the chaincase bearing and the tower bearing to evenly space the jackshaft out. It allows you to shim the jackshaft much closer to proper alignment. In our testing, a properly aligned Ultimax XS821 has lasted 3000 miles of clutch kit testing and trail abuse. This kit includes one 3mm tower shim, one 3mm chaincase shim, one 3mm retainer shim, and complete instructions and alignment specifications.