This 5 Pack of Nylon Twin Wheel casters are perfect for office chairs. 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. We recommend replacing all 5 at a time, as overall heights can vary slightly between manufacturers. Nobody wants a wobbly chair!