This replacement or spare magazine is compatible with your AR-308/308 Cal AR type rifles using LR-308 (DPMS) or SR-25 pattern mags. It is constructed of DuPont Zytel polymer with injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA. NOTE: This item is not compatible with rifle using Armalite pattern magazines. Type Detachable Model Standard Finish Black Series Replacement Magazine Caliber 308 Win Capacity 20 Material DuPont Zytel Polymer Model Fit AR-308