The Trijicon RMR/SRO lower 1/3 co-witness quick release mount features a Mil-Spec drop test rated 7075-T6 aluminum design, with an easy to use one handed tool less mounting system. This return to zero mount boasts a low weight and low profile design, compatible with any picatinny rail. Designed specifically for the Trijicon RMR. This lightweight Lower 1/3 co-witness mount is perfect for mounting the RMR on any rifle platform with a picatinny rail. The AC32075 provides a Lower 1/3 co-witness with backup iron sights. This means that the RMR/SRO is mounted higher than the iron sights resulting in a clearer field of view. The iron sights remain visible in the lower 1/3 of your optical window for use as a backup.Features:Distance from top of mounting rail to optical axis for RMR it is 1.511 inches, for SRO it is 1.752 inchesLower 1/3rd co-witness with iron sightsFits the Trijicon SRO reflex optic, RMR reflex sightMade in USA