TOOGOO(R) Threaded Stem Connector Twin-wheel Black Chair Trolley Caster with 3/8" Threaded Stem Black Double Wheel Straight Threaded Stem Connector Casters. Features double wheel with 2inch in diameter, design with threaded stem connector Threaded Stem Connector Caster made from plastic wheel with metal holder to prevent corrosion. Threaded stem connector size: Approx. 3/4" Tall x 3/8" Diameter Wheel diameter: Approx. 2inch.