Back Up Iron Sight for your AR-15, M4, M16A4. Made by Midwest Industries. CNC Machined from billet aluminum and hardcoat anodized. These High Quality back up iron sights feature an A2 aperture, A2 windage knob, and rugged protective ears. Spring loaded ball bearing locks up on an enlarged surface area, allows this back up iron sight to be deployed in one smooth motion, and stay locked up tight. The locking detent button has a stepped down radius to provide easy operation even in muddy or wet conditions. Made in the U.S.A.