ZEV Technologies Muzzle Device 5.56 1/2x28 Threads. Wrench flats are incorporated for ease of installation.The ZEV Muzzle Device is only compatible with barrels that have a .750 or smaller gas block journal due to the fact that the body of the muzzle device extends over the shoulder of the barrel. Specifications for ZEV Technologies Muzzle Device: Manufacturer: ZEV Technologies Color: Black Gun Model: AR-15 Weight: 4 oz Condition: New Features of ZEV Technologies Muzzle Device Provides flash suppression and muzzle rise reduction Package Contents: ZEV Technologies Muzzle Device Crush Washer What firearm models does the manufacturer say ZEV Technologies Muzzle Device is compatible with? The manufacturer suggests that ZEV Technologies Muzzle Device is compatible with AR-15ZEV Technologies ZMD-556: Muzzle Device 5.56 1/2x28 Threads