The Holosun HE503CU-GR is a 20mm Micro Reflex Sight created with Solar Failsafe™ which means you won't have to worry about battery failure. With the added feature of automatic brightness adjustment, you'll be able to use your red-dot in almost any lighting condition. Add to that the convenience of Shake Awake™, the user-programmable LED shut-off technology that wakes with the slightest movement, and you have one of the most battery efficient micro reflex sights on the market. Topping it off is T6 Aluminum housing and multi-reticle system, making this a must-have optic for any rifle or PDW.