Bond solid rubber wheels are precision molded into a single unit of high grade rubber compound and are furnished with a soft or hard tread. They are available with self-lubricating bushings or straight roller bearings. Roller bearing wheels include end washers pressed into the hub ends to hold the bearing in place. Lubrication is through a pressure fitting in the hollow axle. Soft-tread, Durometer in 75 Shore A: A soft cushion tread is permanently molded to a hard rubber core forming a single unit providing maximum floor protection and quiet operation. The uniform thick cushion tread offers excellent mobility for manually moved loads on hard surfaced floors. The tread is resilient and abrasion resistant, and non-sparking. Hard-tread, Durometer in 60-80 Shore D: Composed entirely of hard rubber, these wheels provide higher capacities, easier rolling, quiet operation and excellent floor protection. Hard tread wheels are non-sparking and perform well on most firm floor surfaces. Bond all rubber wheels are non-marking, non-sparking, resistant to water, oil and most acids and provide good floor protection. Recommended operating range is -20 degree to 160 degree fahrenheit.