*The calcal red dot scope adopts wake-up technology, the red dot will automatically turn off the system after 2 minutes of inactivity, and instantly activate the LED when it moves slightly*Offers optimal visibility in any weather condition, push button controls make it easier to adjust brightness to suit different lighting conditions than knob style controls. With the battery installed, the reflective sight with memory function can use the last brightness setting after power on.*20,000 hours of extended use at the lowest brightness setting, this red dot uses a CR2032 battery, which is much lighter than AAA battery, while offering two height options for this lightweight optic, making it which makes it work to the fullest on any platform.2 MOA 1x20mm Micro Red Dot Scope, Shake Awake Reflex Sight with 12 Brightness Settings, Gun Sight for 20mm Picatinny/Weaver Rail, Waterproof, Black