Made of eco-friendly silicone rubber and ABS + PC material, and with rubber paint surface process. Football grain design has anti-skid protecting effect.Water resistant design ensures the device functions smoothly when it's raining; Shock-proof feature ensures the device work properly even it crashes or drops. With the free hook included, you may hang it on your backpack for long flights, road trips, hiking, camping, or such, handy to carry and charge by solar. The USB ports are well protected by rubber caps, to further keep them away from water and safe to charge smartphones, tablets, or any other 5V USB-charged devices. Please kindly note that it's comparatively slow for the solar charger to recharge itself via solar power, due to the limited surface of the solar panel.