Egw's chamber checkers are machined from solid 6061 t6 aircraft grade aluminum. Our 4- caliber chamber checker allows you to check 9mm, 40 s&w, 45 acp and 38 super with one checker. While some companies use boring bars to make chamber checkers, egw uses the actual clymer reamers that are used to chamber barrels. Anodized matte black for durability.