Need even more run time than the 2600 mAh batteries can provide you? Well here is your ticket. Add this extension tube to your Kill Light XLR250 and increase your battery capacity. This extension will allow you to use an additional 18650 rechargeable battery or 2 extra CR123A batteries. * Only use with single mode one power LED modules! Can damage 2 OR 3 mode XLR250 LED modules!