Micro green dot reflex optic combo for Mossberg 500/590. Includes barrel optic mount w/ additional rails. Mount your optic as low as possible w/ the micro dot base. Unlimited eye relief and Auto ON/OFF brightness sensor. LED (Light Emitting Diode) 100% safe for the eyes. Powered by 3 Volt lithium batteries (CR2032) included. Black anodized aluminum body for quality. In the Box 1X Green Dot Optic 1X Barrel Rail Mount Specifications: California Proposition 65 Warning: Cancer and Reproductive Harm - www.P65Warnings.ca.gov