CVLIFE Red & Green Dot Sight 4 Reticles Reflex Sight ON & Off Switch with 20mm Rail Mount Tubeless design with 33mm reflex lens aperture provides a wide field of view, so this reflex sight is suitable for rapid-firing or shooting of moving targets besides normal shooting. Dual illuminated ( red and green);4 reticle shapes, provide various choices in different occasions, like sunshine, cloudy day. Integral Weaver P-i-c-a-t-in-n-y Rail Base for easy mount on guns with a Weaver P-i-c-a-t-i-n-n-y Rail. Parallax corrected & unlimited eye-relief; Allen head screw type windage and elevation click adjustments, with locking screw Instruction: There are two buttons written on red and on green. When you press the on red button, the red light will on, so does the green light. If you want to turn off the light, you need to press the two buttons together.