This waterproof backpack is equipped with reflective strips and LED lights which will respond to signal received from remote controller, reminding passengers and drivers keep distance from you. Built-in 500mAh rechargeable battery. It can work 20 hours of continuous work after 2 hours full charging. Absolutely a perfect add-on for night safety cycling. Specifications: Material: Nylon 43; PC 43; ABS Color: Gray / Yellow gray ( optional ) Working Time: 20 h Charging Time: 2 hours Battery: 3.7V, 500mAh Bag Size: 44 * 33 cm / 17.3 * 13.0 in Package Size: 41 * 32 cm / 16.1 * 12.6 in Package Weight: 458 g / 16.2 oz Package List: 1* Bag 1 * Wireless Controller 4 * Zip Ties 1 * ManualProducts from GuanGuan's store