3" (75mm) Extra Large Replacement Office Chair Caster Rollers - Standard Wheel (Set of 5) - S5110 Double / twin wheel design with 3" (75mm) wheels Standard 7/16"x7/8" (11mm x 22mm) grip ring mounting stems work in most standard chair bases Hard nylon wheel - Ideal for use on carpeted surfaces, plastic chair mats, etc. Casters with larger wheels are more heavy duty than standard smaller chair casters Black