ProMag RM40FDE Standard 40rd Detachable w/Roller Follower 5.56x45mm Fits AR-15 Flat Dark Earth DuPont Zytel Polymer

This replacement or spare magazine is compatible with your AR-15. It is constructed of DuPont Zytel polymer with anti-tilt roller mag follower and mag spring formed from chrome silicone wire. Made in the USA.