[SAFE PROTECTION FOR All FLOORS]:These office chair caster wheels are encased with an extra-thick polyurethane layer and guaranteed not to scratch or leave marks on any surface even without using a chair mat. 100% safe gliding across hardwood floor, parquet, laminate, linoleum, tile, short-pile carpet. (Not suggest using on the rug with wool over 2cm) [UNIVERSAL FIT(NOT FOR )]:Our Twin Ball Bearing casters office chair swivel wheels are designed with universal standard size rods 7/16 inch (11mm) x 7/8 inch (22mm) stem, heavy-duty design (a set of 5) can support up to 700 lbs. Can rotate on almost any rolling chair, whether it is a luxurious executive leather chairs or office chairs, computer chairs, game chairs. [SOFT & QUIET & SMOOTH ROLLING]: There twin wide transparent Twin Ball Bearing casters precision bearings and a shock-absorbing polyurethane tire can make the casters roll smoothly and easily on any surface without making any sharp sounds or noises. [VERY EASY TO INSTALL AND DURABLE]: Without any tools, pull out the old office chair casters and push in the new wheels to install successfully. At the same time, our transparent polyurethane casters are more resistant to acid, grease, water and certain chemical substances, so that the casters have a longer service life. size: Wheel diameter 50mm Wheel width 55mm Installation height 59mm Insert rod diameter 11mm Height of plunger 22mm Material:PU polyurethane + rubber + metal colour:Black+transparent Package Contents: 5 * Office Chair Casters Wheels Only the above package content, other products are not included. Note: Light 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.