These quality replacement AR-15 pattern standard capacity magazines are constructed from high tech polymer with a high-tensile strength compression spring and an anti-tilt follower. The textured surface provides a positive grip for precise manipulations. Specifications Weight: 0.3lbs Compatibility: AR-15 / M16 / M4 Caliber: .223 Remington / 5.56x45mm Capacity: 30 Rounds Body Material: Polymer Spring Material: Stainless Steel