Injected gray thermoplastic rubber track with PP hubs provides a wheel that is gentle on the surface. The hardness of the track is 85°Shore A and is suitable for indoor use, where you want a quieter, more cushioned ride than you get with hard nylon wheels. Ball bearing wheels provide low rolling resistance and are suitable for continuous operation. The 33 mm diameter wheel has a PUR tread with a hardness of 95° Shore A. Temp.Best.-20°C- +50°C.