Features a standard 11mm x 22mm stem and 50mm dual rubber casters, heavy duty rubber casters designed as replacement wheels for office chairs Each rubber caster can hold up to 70lbs. 5 pack can hold 350lbs max Easy to Install: Simply pull your current casters down and push the replacement chair wheels into the socket, then start enjoying your comfortable working time. PU plastic wheels protect hardwood, laminate, tile, slate and all other hard floor surfaces, carpets without any marks or scratches. Smooth and Quiet Rolling: Dual wheels design allows for super quiet and smooth rolling, no noise when rolling, will not disturb anyone while working. Eliminates the need for expensive ugly plastic floor mats.