DURAMAG MAGAZINE FEATURES: Plastic has proven molecularly unstable in extreme environments, vulnerable to changes in humidity, and unable to retain shape during extended use. This is why this stainless steel Duramag is the one magazine design you can rely on during a sunny day at the range, frozen night on the tundra, in the sands of the desert, or pulling from long-term storage. Duramag SS 7.62x39mm, 20rd is compatible with any AR-15 style firearm. DURAMAG MAGAZINE SPECIFICATIONS: Brand: C Products Defense Inc Caliber: 6.8 SPC Model: Duramag Rifle Series: 6.8 SPC, 22 Nosler Material: Stainless Steel Capacity: 20 rd.