Product details:

Derale, Heavy Duty Flex Fan, 18" HD Flex Fan, 18" Derale Heavy Duty Flex Fan Provides maximum airflow at low RPMs when the vehicle speed provides little or no airflow through the radiator. At higher rpms, the vehicle speed provides ample airflow and the fan blades flatten out to minimize engine loading, increasing horsepower and mileage. Reinforced stainless steel blades for extended life.