【High-Efficieny】The high-efficiency of its three/four solar Monocrystalline panels cell is based on SunPower Maxeon technology, that allows the USB solar charger to reach 25% of conversion efficiency while providing enough power (up to 2.0A max per port or 3.0 A max overall) 【Advanced Smart IC Chip Technology】 The Microchip of solar panel phone charger support to detects the electronic devices plugged into the USB ports for fast charging two phones simultaneously under safe conditions as well as the prevention of overheating 【Portable and Foldable】The 6.3x 11.1x 1.06 inch (when folded ) small size and 17.3-ounce design that can easily squeeze in your backpack offers portability and simplicity, and the attachment hook makes the portable solar charger ideal for connecting to a backpack while you’re on the hiking or walking around town 【Dualable Design】WATERPROOF AND DURABLE - The rugged 600D waterproof PVC canvas material will protect your solar panel when backpacking, hiking, or traveling. Includes two carabiners for easy set up on your backpack or tent. We also offer a “Lifetime Warranty” so any time your solar panel USB breaks down during normal usage we will replace it free of charge. 【Package】21W/28W Portable Solar Charger, 3ft(100cm)Micro USB Cable, User ManualAny cloud or cover may influence the charging speed. Although our solar charger with automatic restart function, we still suggest you to reopen the solar panels and replug your device if the charging is too slow.