Roush Performance 401433 - Roush Performance Mustang Underdrive Pulley

Gain more horsepower, gas mileage, and accessory life with the ROUSH 25% reduction Mustang Underdrive Pulley. This pulley fits 2005-2010 Ford Mustang GTs with the 4.6L engine only, and does not work with ROUSHcharged vehicles.
The ROUSH Underdrive Pulley dampens damaging engine harmonic vibration, meets SFI Spec. 18.1 and has a diameter that is 25% less than stock. The benefit is that 25% less power is diverted to running accessories, such as the alternator. As a result, more power is freed for performance. This part has been found to increase power by 8-10 hp. Due to the increased efficiency, fuel economy is also increased. In addition, because the accessories run by this belt are being run at reduced rate, their longevity is improved.