Dedicated Magpul magazine for rifles chambered in 300 BLK that supports the differing geometries found in that caliber. The result is a more reliable magazine. In addition to the performance gained by a dedicated mag, the PMAG 30 AR 300 B also offers a safer way to feed your 300 BLK rifle. The PMAG 30 AR 300 B's distinct rib design and smoother upper-half texture provides the shooter a distinct visual and tactile difference from any other PMAG to mitigate dangerous cross-loading issues. Features: Capacity: 30 rounds Caliber: 7.62x35mm (.300 Blackout)