3" (75mm) Extra Large Replacement Office Chair Caster Rollers - "Soft" Wheels For Hard Floors (Set of 5) - S5111 Double wheel design with large 3" (75mm) wheels Standard 7/16"x7/8" (11mm x 22mm) grip ring mounting stems work in most standard chair bases Soft nylon tread is better for use on hard surfaces including hardwood floors Casters with larger wheels are more heavy duty than standard smaller chair casters Black