The Roller Derby Wheels set are colorful wheels, that light up as you spin. They come in a variety of colors and you can remove the core to stop the light up feature. They can style you for the arena or make you visible at night. The light up feature does not require charging or batteries, they work solely on the motion. The Roller Derby Wheels sets make a great gift or are cool way for you and your team to standout at matches. The wheels consist of high quality extra grippy urethane, for a smooth ride. The wheels fit any derby skate.