Ending today, Groupon offers a Set of 2 Mathmos Bike Wheel Lights
in White or Multicolor for $16.99
with free shipping
. That's the lowest total price we could find by $12. (It's also an inexpensive alternative to purchasing a Tron Light Cycle.) Sales tax is added where applicable. These screw onto bike wheel valves and create circles of light upon movement. Note that these do not fit racing bike valves.