Polyolefin wheels are a light weight wheel with high shock resistance, excellent chemical resistance, and abrasion resistance. Series 30 casters use tough bright zinc plated components such as heat treated double ball bearing raceways, 5/8" bolted king pin, 1/2" axle bolt, and 1/4" cold forged steel top plate and fork construction. For more caster options, including bearings and top plates, please call our sales team in West Reading, PA, at 1-800-215-8220.