The FAST Micro-SB is specifically designed for the Aimpoint CompM5s, CompM5b and Duty RDS mini red dot sights and features a built-in, fully adjustable front and rear back-up iron sight. The built-in BUIS is a non-standard height (0.95" tall) that does not allow for compatibility with a traditional front post (typically 1.41" tall), so the front post is factory installed. The integrated BUIS are visible under all of UNITY's FTC magnifier mounts. It puts these taller micro sights at a height of 2.26" and comes standard with a 2 cross bolt rail clamp, but is compatible with the FAST QD Lever (sold separately).