The black Boost Solar Backpack from BirkSun allows you to use the power of the sun to charge your devices while on the go. Simply plug a USB device into the sewn in USB connector and start charging. Three minutes of sun exposure will add 1% to your smartphone battery charge. The monocrystalline solar panel is waterproof and prominently featured on the bag for sun exposure. The Boost Solar backpack includes a 15" fleece laptop sleeve, a neoprene organizer sleeve, and exterior pocket for accessories.