Carries higher capacities than rubber, outwears rubber, floor protective and quiet in operation. Duralast Wheels --1/2" thick 95A Poly on Iron Poly-Soft Wheels --1/2" thick 82A Poly on Iron Superlast Wheels --1" thick 95A Poly on Forged Steel Duralast XC & Superlast XC Wheels --70D Poly on Iron/Forged Steel Polylast Wheels --1/2" thick 95A Poly on Alum. Unilast Wheels --95A Solid Polyurethane Poly-Tech Wheels --1/2" thick Poly on Polyolefin