Ford Mustang GT Cobra Billet Aluminum Underdrive Pulleys 01-04 PART #1559 FEATURES: Bolt on 8-10 Horsepower in Minutes Lightweight CNC Billet Aluminum Construction Retains Proper Cooling and Charging Uses Factory Length Belt For 2001 Models See Instructions to Verify Water Pump Style VEHICLE FITMENT: 2001-2004 Ford Mustang GT / Cobra Non-supercharged (2001 models check instructions for water pump identification) Easy Bolt On Power Upgrade BBK performance underdrive pulley kits are designed as direct bolt on replacements for the current factory pulleys and retain full cooling and charging characteristics. BBK underdrive Mustang pulley kits are one of the easiest ways to free up an average of 8-10 horsepower in under 30 minutes. Easy Installation Each kit comes with complete installation instructions and retains the use of the stock length serpentine belt. Fitment Please note that the crank pulley is to be used with existing OEM crank damper (AKA piggy-back style). In 2001 Ford changed the water pump mid year, please verify this is correct kit for your vehicle Emissions Information This part is NOT C.A.R.B Approved and cannot be installed for use on any emission controlled vehicle in California. It cannot be sold or shipped to any California resident or addressee.