Four, specially angled flutes hide nearly 100% muzzle flash, even during full-auto fire, by dissipating gas and retaining unburned powder for increased residual burn. Constructed of the same 8620 bar stock steel used in the manufacture of AR-15/M16 bolts and carriers, then heat-treated to provide a high-strength core and tough, outer shell. Special, helix design helps align exiting barrel gas to improve accuracy with all bullet types. Skirt extension conceals gap between barrel shoulder and flash hider on AR-15, M16, and M4 rifles.  Can be permanently attached to 14.5" long, M4 barrels for an overall length of 16.1".