Ground Support Products offers a variety of casters: No. 8729: OEM, forged steel, pressed steel with sealed base bearing, toe guard (winged) and stair casters. No. 8729: Sealed double-ball race wheel bearings prevent dirt and debris from obstructing movement of caster wheel. No. 8729: GSPs 3.5-mm fork is 1/2 mm thicker than most others. No. 8729: Designed specifically for the roughness of the airline industry.