Check the listing for details. Advanced SilencerCo ASR Style QD Muzzle Brake - .223 Cal 1/2 -28 in. Color: Black, Condition: New. Listed at 65.99 USD. Advanced SilencerCo ASR Style QD Muzzle Brake - .223 Cal 1/2 -28 in. This muzzle brake is for all hunting rifles with .223 caliber / 5.56mm barrels and 1/2 in -28 in thread.Improved muzzle brake design that has the QD interface to adapt to ASR / SilencerCo style devices. Has two optimally placed vertical vent ports for better muzzle control when firing without your device attached. Has an advanced tuned port balanced internal baffle design for superior blast control. Made from hardened alloy steel and black oxide finished for durability.1/2in - 28 in thread for 5.56mm / .223 Remington caliber barrels.Package includes: (1) muzzle brake, (1) packet of shims and installation instructions. Installation instructionsJust like the muzzle brake that came with your device,DO NOT USE A CRUSH WASHER with the installation of this muzzle brake. This muzzle brake has been supplied with 5 shims so you can properly time the muzzle brake for proper orientation. Included are three thicker shims and two thinner shims to fine tune the timing of the muzzle brake. The two relief ports are to be located on the top at the 12 o’clock position. It is strongly recommended to use a high strength or permanent thread locker such as the Red Loctite 262 (high temperature), Rocksett or equivalent (not included) on the threads of your barrel just before installing for a secure hold.