Product Description The ProMag AR-15 5.56mm Roller Follower magazine delivers extended capacity and dependable feeding for AR-15 style rifles. Built with a durable black polymer body and steel-lined reinforced areas, it features a patented anti-tilt roller follower and a precision-wound spring made from heat-treated chrome silicon wire for long-term reliability. Made in the USA and backed by ProMag&';s lifetime guarantee against manufacturer&';s defects. Product Highlights High-capacity 40-round AR-15 / 5.56mm magazine for fewer reloads at the range Patented anti-tilt roller follower promotes smooth, consistent feeding Steel-lined reinforced feed lips and magazine catch area for added durability Proprietary DuPont(TM) ZytelA(R)-based polymer body in black for rugged, lightweight performance Heat-treated chrome silicon wire spring for long-term reliability Specs Brand Name: ProMag Industries Manufacturer Part Number: RM-40-SL UPC: 708279014512 Platform Fit: AR-15A(R) 5.56mm rifles Caliber: 5.56mm / 5.56 NATO Capacity: 40 rounds Color/Finish: Black Body Material: Polymer (DuPont(TM) ZytelA(R)-based polymer) Reinforcement: Steel-lined / over-molded stamped steel feed lips and magazine catch Follower: Patented anti-tilt roller follower Spring Material: Heat-treated chrome silicon wire Country of Manufacture: USA Disclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product&';s manufacturer.