Our Ejection Port Covers are made from stamped cold rolled carbon steel with a heavy Phosphate coating. The Dust Cover is then treated using the ultra durable Cerakote process. These covers fit standard 223,556 AR15 upper receivers. Fits 556, 223, 6.8, 300 AAC, and will not fit RRA 9mm or UMARX 22. Shipping is free in the U.S..