Heavy Duty Casters: 4 inch casters are made by chemically combining a polyurethane elastomer tread with a cast iron core, which offers higher weight capacities while providing good floor protection and a smooth quiet rolling operation. Double Ball Bearing: The heavy duty caster wheel has double ball bearings to reduce vibration for a smooth, quiet, and mark-free gliding experience on a variety of floors. The polyurethane wheels guarantee durability, longevity, and superior roll-ability. Wide Application: Caster wheels heavy duty work well in both indoor and outdoor environments. Cater wheels are very popular in applications such as trolleys, workbenches, toolboxes, platform trucks, speakers, cabinets, stands, furniture, shelves, coffee tables, display/exhibition equipment, dollies, and other common items found in workshops, garages, kitchens, warehouse and offices. Caster Size: Top Plate Caster Dimensions: Length: 3-5/8", Width: 2-3/8". Hole Spacing: 2-3/4" x 1-3/4". Polyurethane caster wheel size: 4" X 1-1/4". Overall height of casters: 5.3". The Heavy duty industrial caster set of 4 are easy to install, so they won't take up too much of your time. High Load Capacity: Each caster can support up to 400 lbs, with a total capacity of 1600 lbs(set of 4). Caster Wheels heavy duty are easy to push and save effort, which are designed for handling. NINOSO Caster Wheels, 4" Heavy Duty Industrial Casters Set of 4 with Load 1600lbs Capacity, Polyurethane Wheels for Cart Furniture(2 Brake & 2 Rigid)