Standard Stem Size Easy be Installation Each snap ring rod on top of caster 7/16 "in diameter and 7/8" in length, This is a standard size for almost all office chair models and brands.(exclude IKEA) without using any tools installation caster, Just pull out the old casters and insert the new precision ball bearings, and twin wide transparent polyurethane design Newly revolutionary casters, precision ball bearings，With more powerful support, the transparent double wheels give more thrust to both sides. The office chair wheel can 360 degrees rotate smoothly and roll smoothly . Enjoy smooth and quiet rolling! the caster encased with ultra-thick clear polyurethane layer material , will relieve the stress of rolling on your office chair , easy rolling while causing no squeaky sounds or noise of any kind. Protect ALL floor High quality twin wide transparent polyurethane general purpose caster can better protect our floor, extend the service life, and not scratch the floor. Stay away from debris, and squeak as you slide. Wide range of use These casters are very versatile in our lives. They can be used in home and office chairs, Internet cafes, shopping carts, dining carts and other office chairs to replace wheels. Give any atmosphere a better life experience.