Our Vented Barrel Shroud – Threaded fits any threaded barrel up to 7/8 inch diameter and is offered in multiple thread pattern configurations. Give your rifle that finished, aggressive look you’ve always wanted Vented Barrel Shroud Features Vented with side holes. Black, hard-coat anodized finish to MIL-SPEC Type III. Quickly and easily threads onto your barrel. Does not lengthen the barrel. Does not quiet the firearm. Made in the USA. Can be turned around to lengthen the firearm if needed Barrel Shroud Measurements We offer multiple measurements and thread options to ensure a proper fit for your firearm. If you’re not sure which options to pick, please contact us. Diameter: Outside 1 1/8 inch Inside 7/8 inch  Overall Length: 4.5″ 6″ 8″ Custom length – under 10″ from shoulder of threads Weight 4.5 inch 2.5 Oz. 6 Inch 3.1 Oz. 8 Inch 3.8 Oz. Threads: 1/2″-28 (fits threaded .22, .223, .556, S&W M&P15-22, Etc) 1/2″-36 37/64-28 (.578-28) “usually for .45ACP or .40S&W or .44 Mag Etc.” 5/8″-24 (fits threaded .300, .308, Etc) 5/8-32 9/16″-24 11/16-24 37/64″-28 M9x.75 RH M14x1 RH M14x1 LH M16x1 LH Custom thread. Please provide your rifle’s thread diameter and TPI in the order notes during checkout. For example, 1/2-28 = .500 inch diameter, 28 threads per inch. M14x1 has a 14mm outside diameter and a pitch of 1mm Since this fits the threads, there is no worry about caliber because the bullet already fits inside the threads.