SunnieDog Office Chair Caster Wheels (Set of 5) - Heavy Duty & Safe for All Floors Including Hardwood - Perfect Replacement for Desk Floor Mat - Rollerblade Style w/Universal Fit - Silver 11mm Strong rollerblade style wheels; safe for all floors, guaranteed not to leave marks or scratches on any surface! Vibration reducing polyurethane tires; give you a smooth and quiet roll on hardwood, tile, concrete, stone, vinyl, & even carpet! Universal stem size; Our caster stem will fit 99% of standard office chairs sold in the USA; (7/16" wide x 7/8" tall) or (11mm x 22mm) Very easy to install; no tools required; install in less than 5 minutes! Heavy duty lifetime warranty; if you do not absolutely LOVE how smooth and stylish your new caster wheels are, we will give you a prompt & courteous refund.