For solid and dependable back-up fixed A2 rear sight, the NcSTAR MARDRS does not take up much of your valuable Picatinny rail space. You can have a back-up iron sight ready to go at a moment’s notice and have space for a red-dot/ reflex/ holographic optic on your AR-15 upper receiver. * The MARDRS will fit virtually all AR-15, M4, and M16 flattop Picatinny rail upper receivers. * A2 rear sight assembly with large and small rear aperture. The A2 rear sight is fully adjustable for elevation & windage with knurled click adjustable controls. * Large steel thumb nut and steel rail clamp for positive & secure attachment to your upper receiver. * Compact enough, where you will still be able to mount a red-dot/ reflex/ holographic optic on your AR-15 upper receiver. * Precision made A2 rear sight. The mount and rear sight is made from high quality aluminum and steel. The MARDRS is 2 3/4” Length X 1 5/8” Height
