This NcStar Ar15 QR Weaver Mount/ Cantilever Scope Mount is made to mount to any rifle scope or red dot sight to your rifle in a number of different configurations. The NcSTAR QR Lever System makes mounting the Ncstar weaver Mount to your flat top simple. The mount rings are 30mm with 1 inch inserts, and the Mount Rear Ring is on a dovetail so you can adjust the spacing for a customized fit. In addition the rear ring is also removable so you can set up your Red Dot Sight to co-witness with your weapon iron sights. Constructed of hard anodized aluminum with solid steel.Features: 30mm mount rings with 1" inserts. Dovetailed rear ring to customize fit Removable rear ring for Red Dot mounting. Black Anodized Aluminum and steel construction.