Specifically engineered for use with heavy subsonic .300 Blackout ammunition (200+ grain), the Lancer L5AWM(R) 300BLK magazine features an updated internal geometry which allows longer heavier cartridges to stack properly, increasing feeding reliability when compared to a traditional .223/5.56 magazine. The outside of the mag body is molded with distinctive .300 Blackout markings and the magazine ships with a contrasting flat dark earth floor plate for easy visual identification.NOTE: These magazines have been specifically designed and optimized to alleviate the stacking and feeding issues commonly experienced when running 200+ grain subsonic .300BLK cartridges in standard .223/5.56 magazines. If you are shooting lightweight supersonic .300BLK ammunition (