The Roller Derby Wheels set is 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 motion. The Roller Derby Wheels sets make a great gift or are a cool way for you and your team to stand out at matches. The wheels consist of high-quality extra grippy urethane, for a smooth ride. The wheels fit any derby skate.