The Rollerboys will make your bike ride so smooth that you will never stop anymore! The composite material is strong and durable and the special teeth pattern makes sure you can shift to a higher gear with the speed of light! The ceramic bearings make sure your pulleys will roll so smooth that you never want to stop riding anymore. High quality pulley wheels are a must have for every serious bike rider, with the RollerBoys Ceramic you are good to go!