The HELIUM Jam Wheels are the result of a long term research project which has produced very High Performance Indoor/Outdoor wheels. Helium Wheels are specifically designed for Roller Derby and Jam Skating, where Hi-Rebound and Good Roll are needed in combination with incredibly Tight Grip. (High Rebound means the wheels can roll over some small obstacles or rocks without stopping cold.) What a smooth ride! Roll-Line has developed this wheel giving it properties that are normally not achievable in the one wheel, Super Tight Grip and Good Roll