The Sandberg Solar Charger 21W 2xUSB is a highly efficient solar panel that converts sunlight into electricity. It has 2 USB sockets which can be used to charge your USB devices such as smartphone, tablet or power bank. By connecting to a power bank, you can store the electricity there for charging your smartphone later, or you can use it as a stabilization agent during charging (if your power bank supports simultaneous power input and output). The included carabiners can be used, for example, to attach the solar panel to your backpack when you're on an adventure. This is green energy for your equipment!