Do you have Mountain bike? Are you going to ride a ride? Then you want safety. Deemount tail light is the best for it. It is powered by rechargeable battery. You can easily recharge by using usb. You can use seatpost Placement for mounting this lovely light. You can see white surface light. When you are using this you can get more experience with 4 modes. It is powerful with 100 lm leds.