TUFF ZONE AR-15 / M16 Single Plane Dual Aperture Rear Flip Up Sight Flip Up Rear Sight for Flat Tops, Upper Receiver Precise MOA Windage Adjustment Dual Apertures with the Larger Rapid Target Acquisition Aperture for CQB Operations and the Smaller Precision Aperture for High Accuracy Aiming Operations Compact in Size, Allow User to Attach other Applications in the Front