This is a direct-fit, bolt-on Flex-A-Lite® S-Blade dual electric-fan system for new body style 2001-2005 Chevrolet and GMC trucks with the 6.6L Duramax diesel. Dyno tests show a gain of up to 27 horsepower and 34 lbs-ft. of torque while also improving fuel economy by replacing your stock clutch fan assembly with this dual electric fan system. This system features two 15-inch electric fans and a Flex-a-lite Variable Speed Controller that varies the fan speed from 60-100 percent, depending on radiator temperature. These powerful fans move up to 6,000 cfm of airflow!