Lumify uses an innovative new tube design which guarantees unrivalled waterproofing. The battery compartment, power switch, mode switch and USB charging port are all protected under an o-ring sealed screw cap which offers bottle-tight waterproofing.Lumify are USB chargeable which means you can use them inside your home as well as outside. USB also gives you the option to fully charge your lights in time for a party if the weather has let you down in as little as 3 hours from flat.