The Echo 1 Red Star CPM CQB Flash Hider is the perfect custom AEG style muzzle brake for your airsoft gun. Fits on 14mm negative CCW threaded barrels. Fits directly on 21mm E&L AK rifles too, with its adapter. So it fits both 14mm (with included adapter), and native 21mm specifically for E&L AK rifles (all Gens). All metal construction, black only.