The Holosun SCS-320-GR (Solar Charging Sight) is designed for P320 optics ready handguns or other DPP footprint applications. It is designed to attach directly to the slide without an adapter plate and uses our innovative solar charging system with multi-directional light sensors to automatically adjust brightness in dynamic situations., The SCS can potentially operate indefinitely using an internal, rechargeable 20,000-hour battery meaning under even moderate exposure to bright light, you will never need to change batteries again. The SCS also includes an intensity override function which locks the optic into a high brightness mode for 30 minutes and a low power indicator which warns of low battery days before charging is needed., Note: The internal rechargeable battery is not removable., Brightness Override – In very dark conditions, the optic will reduce brightness to a low level to match the ambient light. If the user wants a brighter reticle, they can press the function button once to raise the brightness to level 9 -12 for 30 minutes. This is ideal when shooting from a covered location on a sunny day to ensure the reticle is not washed out., Low Battery Level Indicator – On start up, the SCS will report if the battery is low for the first 10 seconds of operation. If the battery is below 20% it will Flash once (within 1~2 seconds) for 10 seconds, if it is below 10% it will Flash twice (within 1~2 seconds) for 10 seconds. Lastly, if it is below 5% it will Flash 3 times (within 1~2 seconds) for 10 seconds.