Type #304 Stainless Steel Casters are ideal for food processing plants, laboratories, hospitals, or other wet or corrosive environments. Feature 1/2" king pins, double ball-bearing raceways, and grease seals in upper raceway. Choose either casters with 2-3/4x3-3/4" top plate with 1-3/4x2-7/8–3" bolt holes and 3/8" axle and lock nut or casters with 4x4-1/2" top plate with 2-5/8x3-5/8–3x3" bolt holes and 1/2" axle and lock nut.Wheel type codes are:PO–polyolefin PH–phenolicSPU–solid polyurethanePR–Performa rubberPPU–polyurethane on polyolefin