Caspian Arms Trademark CO2 compatible Very solid and heavy pistol from this Taiwan manufacturer. The Caspain Hi-Capa 5.1 is based on Marui Hi-cap 5.1's design. Full metal construction with 20mm lower rails for installing accessories such as flashlight & laser unit. From the minute you rack the slide, you'll know you've got a serious piece in your hand. The blowback action and recoil add to the reality! Metal slide makes this pistol extremely heavy and solid with a strong kick during blowback.