RWM Casters UIR-0415-06 4" Diameter X 1-1/2" Width Urethane on Iron Wheel with Straight Roller Bearing, 600 lbs Capacity 3/8" Axle diameter, 1-7/8" hub length, 600lbs capacity^Urethane iron wheel with straight roller bearing^92 Shore a durometer hardness^Temperature range from -40 degree F to 180 degree F