Get Your Timing Right. SureFire SOCOM shim kits help ensure precise timing of SureFire SOCOM muzzle devices on a rifle barrel. Each kit includes shims with different thicknesses. The shims can be used alone or combined to achieve proper muzzle device alignment. Constructed from 300-series stainless steel for durability and long service life. Shims are color-coded-no need to measure to ensure proper thickness.