The HE507C-GR-X2 is an open reflex sight designed for pistol applications. Features Holosun&';s Multiple Reticle System giving the user three different green reticle options. This sight is powered by a high-capacity CR1632 battery to power the LED for up to 50,000 hours and features a convenient side access battery tray, allowing the user to change the battery without removing the optic. In the event you do run out of battery, this optic features Solar Failsafe technology to power the optic when used in sunlight. Holosun also designed this optic with Shake Awake technology that senses motion to power the LED on and off, and a last setting recall that ensures you don&';t lose your custom settings when the unit powers down. This item is IP67 waterproof rated.