The HS515GM is a ruggedized micro red dot sight with the option of a 2MOA dot only or a 2 MOA dot with a 65MOA circle reticle pattern. Employing new LED technology the life time for one CR2032 battery can reach 2 years if left on constantly. However the shake awake feature also works to extend the battery life. The M signifies extra rugged features including a CNC milled 7075 Aluminum housing pressure tested for submersion up to 30 meters for 30 minutes and a snag free housing design that protects the windage and elevation turrets. This product includes clear flip-up lens covers a quick release mount and a kill flash filter. - Features - Shake Awake