This replacement or spare magazine is compatible with your AR-15, M16. It is constructed of DuPont Zytel polymer with injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA.
Specifications:

Caliber	223 Remington/5.56 NATO
Capacity	42
Finish	Black
Model	AR-15
Material	Polymer
Type	Detachable
Model Fit	AR-15
Brand Fit	AR-15 Platform
Max Capacity	42