The 30 Watt is designed to provide electricity for mobile devices people use in daily life. When unfolded and exposed to sunlight, it's able to charge cell phones, laptops, GPS, PSP, digital cameras or other devices via USB connection conveniently. This solar bag can be universally used in all kinds of outdoor activities like expedition, camping, traveling, exploration, etc. The 30w is a favorite of mobile users needing to keep their laptops powered. Learn more detailed information, please click here: http://www.sygdcigscell.com/outdoor-modules/portable-solar-charger/30w-cigs-flexible-portable-waterproof-solar.html