IPX4 water resistant-highly airtight construction, stronger waterproof. This taillight is water-resistant for any weather, extremely durable. USB rechargeable-this taillight can be charged by USB cable via computers, Chargers, or portable power bank. This will save you lots of money on batteries. Easy to use-hook onto your belt, running gear, reflective vest, backpack, dog collars, harnesses, or anywhere on your clothing. Mount to your bicycle, helmet, skateboard, scooter, stroller, wheelchair, or anywhere you can imagine.