AngryGun Barrel Nut Shims/Washers (Includes 0.5mm x 5pcs and 1mm x 5pcs) - Airsoft Shop, Airsoft Guns, Sniper rifles, Airsoft pistols, parts and bbs by FireSupport
DYTAC Barrel Nut Adjustment Shim Set (30pieces)
AR Solutions AR15 Barrel Nut Shim - 10 Count - Black | Sportsman's Warehouse
AR15 Barrel Nut Shim for Free Floating Handguard by GunTec