POLYURETHANE TREAD: Heavy duty caster is made of a polyurethane tread on cast iron core for long life and keep all floors clean and free of tread marks. The combination of flat tread and high-quality polyurethane can withstand heavy loads and frequent use. Total Lock Brake: The brake locks both the wheel and the swivel simultaneously, which makes it safer when used as a rolling bench caster, industrial caster, or heavy-duty caster, especially on uneven surfaces. Polyurethane wheels have excellent floor protection and easy rolling properties. HEAVY DUTY LOAD: Industrial casters are made of high-quality polyurethane and galvanized thickened yoke, with strong load-bearing capacity. The sturdy material allows you to move heavy loads with ease and safety. Each caster holds a maximum of 800 lbs.(Sets of 4 load 3200lbs) NO-MARKING & SMOOTH: Outdoor caster wheels design with roller bearings, these wheels guarantee durability, longevity, and superior roll-ability. Mark-free gliding experience on a variety of floors. WIDE APPLICATION: Industrial caster wheels heavy duty are mainly used in outdoor or indoor. Widely used in tool box, workshop table, steel table, dolly, workbox, dumpster, trolley, institutional equipment and cart. NINOSO 4" Heavy Duty Casters Set of 4, Swivel Industrial Caster Wheels with Brake, Each Caster Loads 800lbs (4 Total Lock Brake)