All red dots are not created equal. The FreedomA(R) RDSA(R) (red dot sight) changes the game when it comes to consistency and durability in a red dot sight. It's everything you need in a red dot and nothing you don't. The BDC model comes with a pre-calibrated dial for 5.56/223 55gr rounds that lets you accurately adjust the dot out to 400+ yards. Your battery should be the last thing you have to worry about in the field. That's why Leupold designed Motion Sensor Technology (MST(TM)) to extend your battery life. It automatically deactivates the illumination after five minutes of inactivity, and as soon as movement is detected, the illumination instantly reactivates, Mfg: Leupold