The Quantum Storage Systems WR-00HS Thermoplastic Resin Stainless Steel Casters with Zerk Grease Fittings are a set of four swivel casters designed for mobility and transportation applications. With stainless steel construction and Zerk grease fittings, they offer durability, corrosion resistance, and smooth movement. Each caster can support up to 300 lbs, making them suitable for heavy loads and converting shelving units into mobile ones. The inclusion of brakes on two of the casters provides added stability when needed.