This PWS shim kit is a replacement for the peel washer and is used for mounting muzzle brakes and flash suppressors. New muzzle brakes normally supplied with the necessary washers, nuts, or shims; however sometimes replacement washers are needed if one is damaged or if installing a muzzle device on a different gun. While Peel washers require you to heat them and then peel off separate layers of the washer to get to the desire thickness, a Shim Kit is much simpler. There is no heating or peeling of layers needed. Just install the necessary combination of shims to get the precise alignment you need. Each shim set ships with QTY 1 of Shim 1 (largest), QTY 8 of Shim 2 (medium), and QTY 1 of Shim 3 (smallest). The large shim can be used to give the installer one half of a rotation or as a spacer for barrels that do not have relief cuts behind the threads. Shim 2 is used in varying quantities to achieve the proper alignment of your muzzle device. This shim gives the installer approximately 45 degrees of rotation. If needed, Shim 3 can be used where smaller degrees of rotation are needed for proper alignment. NOTE: All PWS muzzle devices ship with appropriate hardware, these do NOT need to be purchased in addition to a compensator. These are for spare parts kits and other uses.