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

Caliber	6.8mm Remington SPC
Capacity	27 rd
Finish	Blued
Model
Material	Steel
Type	Detachable
Model Fit	AR-15
Brand Fit	AR-15 Platform
Max Capacity	27