This Hydra® Modular Lower comes complete with an AR Interchangeable Magazine Well and offers the ability to change Magazine Wells on your Lower Receiver to accommodate whatever caliber you want.  Ideally suited for use with the Hydra® Quick Change Barrel Upper Receiver (QCB-D), where you can change calibers by switching out barrels as well.  This Modular Lower Receiver includes the Complete Lower with a Six Position B5 Collapsible Stock with Buffer and Main Spring, Complete Fire Control Group (FCG), B5 pistol grip and an AR Interchangeable Magazine Well.