FAULTLESS Thermoplastic Rubber Casters provide a soft, cushioned, non-marking ride. Resist chemicals, caustics, oils, acids, and wear. Thermoplastic rubber surrounds a rugged polypropylene hub that will not dent, mar, fade, or stain. Tread and hub are double bonded and mechanically interlocked to eliminate tread separation. Precision ball bearings. Swivel casters have total lock.