The SCS-VP9-GR (Solar Charging Sight) is designed for the H&K VP9 optics ready handguns. 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. IP68 waterproof.