Add a little extra excitement to your cat's exercise routine with a set of light-up LED inline wheels! These custom wheels light up in a vibrant combination of red, green, and blue when the big wheel spins. No batteries needed—the LED wheels use the centrifugal force of the spinning wheel to create the electricity used to power the LED lights. This kit comes with everything you need to swap your default inline wheels for the LED version. Some hardware parts may be redundant with what you originally received with the exercise wheel and can be kept as spares. Cat Exercise wheel not included. These inline wheels are designed specifically for use with One Fast Cat's Generation 7 Cat Exercise Wheel, and will not work with other brands or older generations of cat wheels. Inline wheels are made of soft polyurethane. High-precision ABEC-7 ball bearings ensure a smooth and quiet ride.