Forward Controls Design Muzzle Brake 1/2x28 QPQ Black. 1215RF has external 0.900 x 24 threads compatible with sound suppressors with 0.900 x 24 threads (such as CGS and Plan B) and adapters such as Rearden's Atlas adapter. Do not use a crush washer if this is going to be a suppressor host. Specifications for Forward Controls Design 1215RF Muzzle Brake: Manufacturer: Forward Controls Design Color: Black Finish: QPQ Fabric/Material: 17-4PH Stainless Steel Threads per Inch: 1/2x28 Length: 1.725 in Weight: 2.17 oz Package Contents: Forward Controls Design 1215RF Muzzle Brake Single use packet of Rocksett Forward Controls Design 1215RF: 1215RF Muzzle Brake 1/2x28 QPQ Black