Designed to fit your AR-15/M16, this ProMagA(R) Replacement Magazine will provide guaranteed reliability and smooth-feeding action for your favorite firearm. Durable DuPontA(R) Zytel polymer construction with 42-round capacity. For use with AR-15 and M16 rifles 5.56x45mm NATO/.223 Remington 42-round capacity DuPont Zytel polymer construction Heat-treated chrome-silicon springs Order today!