The Io USB Tail Light from Portland Design Works comes with two bright LED bulbs that alert following traffic of your presence. There are three modes: steady, flash, and pulse, ensuring you have the right setting for any situation. It can be mounted vertically or horizontally on your seatpost or seatstay, and includes brackets for both. The USB rechargeable battery is fully charged in 2. 5 hours, making this light an impressive value for commuting and road cycling.