Aim faster with the Primary Arms GLx MD-21S Micro Red Dot. Their most advanced micro red dot. The GLx MD-21s features a blazingly bright emitter, intuitive push-button controls, and a powerful solar cell that can fully illuminate your optic from sunlight alone.FeaturesSolar Power Acts as Optic's Primary Power Source in Normal Lighting ConditionsMulti-Select ReticlePush Button ControlsMicro Red Dot Footprint COmpatible with Most Aftermarket Mounts and Risers