4″, Gray, TPR, Swivel Plate Caster With Side Grip Brake, 246 Lb Load Capacity, Quiet & Non-Marking, Effective Gripping Action Across The Tread Prevents Wheel From Rolling, Gray Thermoplastic Rubber Tread On Black Polypropylene Hubs, Offers A Soft, Quiet & Cushioned Ride, Excellent Flat Spot Resistance & Is Resistant To A Broad Range Of Chemicals, Acids, Solvents & Detergents, Bulk.