The Serfas TL-ST Seat Stay light is made up of one 1/2 watt super bright red LED and six 4mm red LEDs. Take it from a bunch of jaded bike shop employees this thing is really bright. It has 3 modes steady, flashing, and what we like to call seizure inducing. The water resistant silicone body will mount to any tube on your bike.
Run time is 100 hours on the included CR2032 batteries.