These Nylon Twin Wheel casters with brakes are perfect for office chairs and carts. The 7/16" diameter stem (see second image for detailed drawing) is the most common size on the market, 3/8" is available as well. These casters are rated for 75lbs each, so on a chair with 5 casters, you have over 300 lbs of load capacity. The bodies are designed to take common abuse from office and shop environments.