About this item 500LB SET CAPACITY (250LB/WHEEL) Heavy-duty 4"" PU casters support 250 lbs per wheel (500 lbs/set) – rigorously tested for industrial carts, machinery bases & heavy equipment mobility. SOLID CONSTRUCTION & FLOOR SAFE Reinforced grey polyurethane (PU) wheels resist oil, abrasion & cuts. Non-marking tread protects wood/tile/concrete floors – no scratches! BEARINGS REPAIR KIT INCLUDED Each set includes 2 casters + 2 mounting nuts + bearings maintenance kits. Simplify long-term upkeep & reduce downtime. UNIVERSAL STEM MOUNT (3/8""-16 THREAD) Standard male threaded stem (Ø 0.6"") fits most carts, dollies & equipment. Included nuts secure installation in minutes. DUAL BALL BEARINGS FOR SMOOTH ROLLING Industrial-grade bearings ensure fluid 360° rotation under heavy loads – no wobble or sticking on flat surfaces.