Machined from tough aluminum, these pulleys hold up to all the abuse racing dishes out. The upper pulley fits a 5/8" or a 3/4" water pump shaft. The combo is complete with upper and lower pulleys & matched heavy duty belts. This combo is available for short or long water pumps & in a 30% or a 1 to 1 ratio reduction. The 1 o 1 ratio pulleys are for low rpm racing, where your motor is not turning the fan enough rpm’s to keep it from running hot.