Constructed of durable, yet lightweight 6061-T6 aluminum with a Type III hard-coat anodized finish, the Duramag® AR-15 .223/5.56mm/.300BLK 10/30-Round Aluminum Magazine offers superior corrosion resistance and lasting performance in harsh environments. The chrome-plated steel spring, coupled with an anti-tilt polymer follower, ensures reliable feeding performance, while the enhanced interior and exterior geometries deliver a precise fit for added reliability. Plus, this magazine is crack-, swell-, and crush-proof for superior durability.