Ultimate Arms Gear Pistol Handgun Black Phosphate Coated Steel Thread Protector Cap Made in The USA For .578-28 TPI Thread Pattern 45 Cal Glock 21 30 36 37 38 39 .451 Bore & Smaller Designed to Protect Barrel Threads when not using a Muzzle Brake or and Device. Machined from Black Phosphate Coated Steel and Knurled for a Positive Grip to Assist in Installation and Removal. Dimensions: 0.69" Diameter x 0.46" Long. Weight: 0.4oz. Small & Compact Highly Effective. Designed in and Made in USA with USA Steel!