Designed to fit your AR-15 pattern firearms chambered in 5.56x45mm or .223 Remington, the KCI USA KCIMZ036 AR-15 50rd Drum Magazine features a clear polymer body that allows you to actively monitor your ammunition. A high carbon steel spring assists the linked follower to facilitate quick and easy loading. This magazine is not compatible with some AR-15 / M16 / M4 receivers that do not have the same internal and external dimensions of a mil-spec lower receiver.Key FeaturesClear Polymer Body: Allows for easy monitoring of ammunition levels.Capacity: Holds up to 50 rounds of 5.56 NATO or .223 Remington ammunition.