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 featuring upgraded mounting hardware for guaranteed rigidity and precision when needed most. The upgraded LED emitter offers complete night vision compatibility as well as a true Red Dot Bright reticle with an ultra-long runtime for full operability in any environment. Additionally the Autolive technology shuts off the reticle when no motion is detected for two minutes and immediately turns on as soon as you pick it up. This Primary Arms red dot sight is part of the SLx optics line. SLx optics have built a reputation for innovation reliability and value. All SLx optics undergo rigorous field-testing during development to best serve you in any environment.