Flex-a-lite's rugged new Monster direct-fit electric fans were designed specifically for the cooling demands of big trucks. Vehicles equipped with these fans have recorded gains as high as 17 HP and 20 ft.-lbs., with a 2-3 mpg improvement. Other features and benefits include dual 15 in. diameter fans, a glass-reinforced nylon shroud, a variable speed control, quicker warms-ups and cool-downs, quieter operation, and a whopping 5,500 cfm maximum airflow rating. All necessary mounting hardware is included for installation. This product ships in approximately 1 days