- Medium hardness, 70-80 Durometer.
NOTE: Small wheels need to run slower due to the high RPMs. Use caution and slower speeds to prevent damage. Monitor the heat to determine the best speed for a specific wheel diameter. Smaller wheels require slower speeds to prevent over heating. Operate at a speed that keeps the bearings cool enough to comfortably touch. By monitoring the bearing temperature, you will be able to run the wheels at a moderate speed continuosly, and faster speeds for brief periods. Do not allow the bearings to become too hot to touch with your bare hand.