STANDARD AMERICAN STEM SIZE 3/8”-16UNC x 1”: Screw diameter 3/8 inch, screw Length 1 inch. Each set of 4 stem casters comes with included mounting hardware, 4 x nuts, 4 x washers plus 1 spanner which help you make a quick assemble. A solid solution for easily positioning your steel stand to any desired area, these threaded stem casters are must-haves for many DIY lovers. STURDY CONSTRUCTION CASTERS SET OF 4 HEAVY DUTY: Housing made of heavy duty steel for high load, adopted industrial-grade electrophoresis plated steel, precious ball bearings, is extremely hard wearing and resistant to dirt. Each 4 inch caster supports 550 lbs. of load (with a 2200 lb. total capacity for four wheels). The swivel casters make the work labor-saving and much more easier to finish. SMOOTHER MOVE & LOWER NOISE: The wheels for cart are made of unmarked high shock absorption polyurethane, can reduce vibration, smoothly moved with no marking, won't harm your wooden floor, no noise, the surface of the 4 inch caster wheels is soft and better protects the ground including wood, hardwood, laminate, vinyl, tile and carpet floors. SAFETY DUAL LOCKING SYSTEM: Upper and lower raceways filled with high-quality swivel bearings that enables the cart wheels to rotate 360 degree smoothly, swiftly, flexibly and silently. Besides, double lock mechanism locks both the wheel and the swivel bearing at the same time, which is essential for safety. MULTITUDE OF USE: These thread stem casters set of 4 are widely used, quickly attach to generally used for workbench, cart, trolley, shelf, wooden cabinet, furniture, home appliances, etc. Whatever your workplace needs assistance making mobile, our caster wheels are a quick fix. 1