400 Series, 4", Polypropylene Rigid Plate Caster, 275 LB Load Capacity, Plate Size Of Holes 1.75" x 2-15/16", Rubber Tread On Black Polypropylene Hubs, Offers A Soft Cushioned Ride & Are Quiet, Excellent Flat Spot Resistance & Is Resistant To A Broad Range Of Chemicals, Acids, Solvents & Detergents, Non-Marking, Performs Well In Wet & Corrosive Conditions, Very Good Floor Protection & Impact Resistance, Temperature Range 180 Degrees Fahrenheit To -40 Degrees Fahrenheit, Durometer 80A + -5, Bulk.