Upgrade your AR15 with the QUATTRO-15 Lower Receiver by DesertTech. This drop-in lower is compatible with all standard AR15 upper receivers, and allows your AR to accept DesertTech’s QUATTRO-15 53 round magazines, as well as standard AR-type magazines with the use of an adapter. The only proprietary parts are the magazine release and bolt catch, the QUATTRO-15 Lower Receiver is compatible with all other standard AR15 parts. Features of the QUATTRO-15 Lower Receiver: Compatible with all standard AR15 upper receivers Allows the use of DesertTech’s QUATTRO-15 53 round magazines Only proprietary parts are the magazine release and bolt catch, compatible with all other AR15 parts Can accept standard AR15 mags (with the use of an adapter) Desert Tech Quattro-15 Lower Receiver Assembly QTR-LR-15