Product Description Rugged Suppressors, Shim Kit, For Aligning Muzzle Devices, Fits 3/4x24 or M18X51 Muzzle Threading Rugged Suppressors SA017 Shim Kit 338 Cal (6.8mm) for 3/4"-24, M18x1, M18x1.5 tpi (3 Sizes) at Shooting Surplus $15.00 Buy Now Check Price on Amazon Check Price on eBay