Designed for the Rock and Roll trainers. The turntable riser is designed to meet the needs of riders who want a level bike when they train. The Riser Ring is adjustable to four heights to simulate flat roads on almost any bike. Sits under front tires for a stable ride, no matter how hard or long the workout, with the addition of a swivel base allowing the front wheel to move freely. It has a swivel base. This is to compensate for being able to stand up and kick like you can on the Rock and Roller. This enables the front fork to turn and help dissipate some of the twisting load on the front forks.