The Unity Tactical FAST Optic Riser securely elevates direct-to-rail mounted red dot optics with a standard lower 1/3 co-witness picatinny mount to a 2.26a ^2 optical center line. The FAST Optic Riser provides an elevated M1913 Picatinny platform for direct attachment of optics, such as EOTech EXPS, Vortex UH-1 and other lower 1/3 co-witness optics.It comes standard with a two cross bolt rail clamp and is compatible with the FASTQD Quick Detach Lever (Not Included).If you're running an absolute co-witness height optic, you need the FAST Absolute Riser.FAST is a series of optic mounting solutions that provides end users with a quicker sight picture than standard height mounts. FAST mounts create a 2.26" optical centerline from the rail, which allows for more rapid visual processing of the battlefield by ensuring an ergonomically correct heads-up posture. Further, they provide faster and easier dot/reticle acquisition while wearing night vision goggles, protective masks...