STANDARD SIZE- Our caster wheel rollers fit most office chair models available, Standard stem diameter: 7/16 inch (11mm), stem length: 7/8 inch (22mm),Office Chair Caster Wheel Maximum Weight Rating: 50KG each wheel. EASY INSTALLATION- Just pull out the old chair wheel and it out, then push the rod of the new office chair wheel into the slot until it is firmly fixed. It's like changing into a new chair. HIGH QUALITY WHEELS- Made of high quality polyurethane. wear-resistant, light weight, easy to replacement and use, can protect hardwood, laminate, ceramic tiles, and all other hard material floors from damage and scratches, chair wheel are always and easy to control when rolling. WIDELY APPLICATION- Suitable for most office chair,computer chair, gaming chair,executive chairs, work chairs, rolling stools, easy to slide on the hard floor made of carpet and polyurethane material, very suitable or office use. Color: Black Material: nylon Package Contents: 5 x wheels Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.