SUPER CUSHION rubber caster wheels provide a cushioned ride, shock absorption and quiet operation. They can be used outdoors on grass or dirt but are not recommended for use on gravel or sand. Super cushion rubber wheels are nearly as resilient as pneumatic wheels with none of the maintenance problems associated with air filled wheels. The absence of air in the tire eliminates the risk of a flat tire. SUPER CUSHION rubber caster wheels are known for their noise absorption and shock isolation. They have an extra resilient soft rubber tread bonded to a thick aluminum wheel center. They are especially popular for use in Hospitals, Scientific and Electronic Laboratories, Department Stores, Hotels, TV and Movie Studios - wherever noise and vibration should be eliminated. They are ideally suited for moving fragile or delicate cargo. This Super Cushion rubber wheel is featured in our Caster Model 9. We recommend the casters with gray soft rubber tires because they are a non-marking material.