These caster wheels have gray non-marking injection molded thermoplastic rubber tires mechanically bonded to a polyolefin ( industrial plastic ) center. They are popular on equipment in Pharmaceutical Laboratories, Hospitals, Food Service and other Institutional applications. These caster wheels provide a softer ride than polyurethane and yet withstand exposure to many chemicals and solvents. They can be used in industrial applications which do not involve shock, overloading, abuse, obstructions, poor floors or storage (standing) loads.