JMac Customs 4C 1/2-28 4-Port Muzzle Brake with KeyMount Black Nitride Black. The best of both worlds Our super effective RRD4-4C muzzle brake comp with KEYMO suppressor mount These are designed to install with a shim kit on standard shoulder mount style barrels (factory muzzle device installed with crush washer) and can be permanently attached using the (optional) pin. Specifications for JMac Customs 4C 1/2-28 4-Port Muzzle Brake w/ KeyMount: Manufacturer: JMac Customs Color: Black Finish: Nitride Fabric/Material: 17-4PH Stainless Steel Threads per Inch: 1/2x28 Gun Make: Kalashnikov Length: 2.82 in Weight: 3.84 oz Condition: New Features of JMac Customs 4C 1/2-28 4-Port Muzzle Brake w/ KeyMount 4 Port Muzzle Brake Package Contents: JMac Customs 4C 1/2-28 4-Port Muzzle Brake w/ KeyMount JMac Customs RRD-4C-28S-KM: 4C 1/2-28 4-Port Muzzle Brake with KeyMount Black Nitride Black