The R.EX Riser is a low profile, lightweight riser for AR platforms. Set at the ideal height for co-witnessing while using the SI Reflex Exoskeleton mount with either A2 height, or Sidewinder sights (without spacer), the REX Riser is versatile and provides and solid mounting platform. While optimized for use with the R.EX Mount, the universal Picatinny pattern can be used with many other optics that can be mounted on picatinny sections. Picatinny rail features 3 slot design.