Giant's Numen Plus Aero Taillight is small, powerful and impressively bright. It's so sleek and light that it almost disappears. Come nighttime, though, cars will notice its three bright LEDs. It has a run time of up to 10 hours on its USB rechargeable battery, and features a steady mode and two flashing modes. The flexible rubber mount easily attaches to most seatposts, including aero and integrated models.