The Empire BT-4 Combat has an Adjustable vertical front grip. Selecta-Barrel adapter allows use of multiple barrel threads, M-4 style raised rear sight/carrying handle, M-4 style barrel system, Modular trigger system, Dual picatinny mounting rails meet military standard 1913, Easily accepts expansion chambers, vertical & horizontal bottle adapters, Works with CO2 or compressed air. Manufactured by Empire.