Dial 6149 Motor Pulley, 1/2 in Dia Bore, 3-3/4 in OD, ZincVariable pulleys must be opened 2 1 2 to 5 in full turns, depending on air resistance or motor will overheat. If motor cycles, open variable pulley until motor stops cycling. If cycling persists when pulley is fully opened, you must use the next size smaller pulley. Always use pulley size recommended by cooler manufacturer. Unit: EA UPC: 026529614900 Model Number: 6149