PowerGreen Solar Charger with Dual USB 21W Foldable SunPower High Efficiency Outdoor Solar Panel for Cell Phones and All 5V Digital Devices High Conversion Efficiency: Sunpower mono-crystalline solar panel increases conversion efficiency up to 24% which is much higher than common solar panel charger. Dual USB Outputs: Provide enough power to charge two devices at the same time when you run into embarrassing power outage moments. Highly Portable: Foldable design for easy carry and transport, water resistant to endure all weather conditions, great for nature trips, hiking, picnic, sailing or other outdoor activities (Water resistant for the main body of the panel, not including the USB output ports). Slim and Powerful: 1/3 lighter than the same power of solar silicon. The total power increased by 1/3 in compare with the same solar panel size; eye-holes enable easy attachment to backpacks while camping. Incredible Durable:Industrial-strength PET polymer faced solar panels sewn into a rugged polyester canvas offer weather-resistant outdoor durability.