Increase boost and add tire shredding horsepower! Steeda's supercharger pulleys directly replace the factory supercharger pulleys and gives approximately 1-5 psi of extra boost. Steeda Pulleys are the best available featuring drilled holes to lower rotating mass, and made of billet steel, not aluminum like others on the market and nickel plated for durability and great looks. In house testing has shown increases of over 125 HP and 100ftlbs of Torque to the Rear Tires!!! (Test on GT500 with Steeda CAI, Pulley and Tune)