Primary Arms SLx MD-21 Microdot, 21mm Objective, 2 MOA Red Dot, Red Dot Reticle, Aimpoint Micro Footprint, Mounts to Picatinny, Anodized Finish, Black SLX-MD-21 The SLx MD-21 is an advanced micro dot sight that incorporates the latest technologies and materials to deliver exceptional CQB performance. Weighing only 5 ounces, the SLx MD-21 is both lightweight and rugged, with upgraded mounting hardware for guaranteed rigidity and precision when you need it most. If you are looking for a taller mount, check out the SLx 2.26" Mount for use with night vision or to achieve a more heads-up shooting position. The upgraded LED emitter offers complete night vision compatibility and a true Red Dot Bright reticle with ultra-long runtime for full operability in any environment. Additionally, Autolive technology shuts off the reticle when no motion is detected for two minutes and immediately turns it back on as soon as you pick it up.