This Folding Front BUIS (Back-Up Iron Sight) is compatible with MIL-spec height front AR sights. It locks down, and can be deployed with the push of a button. It is perfect for M4/AR-15 platforms with quick detach optics mounts. • Optimized for AR platform• Compatible with MIL-spec height front AR sights• Single “hybrid” aperture for simplicity• Locks into stowed position with push-button-actuated spring deployment• Aluminum sight blade/aperture and polymer base for optimal strength-to-weight ratio