Increases performance by reducing the engines spinning weight and also because they underdrive the ancillaries (a/c, alternator, p/s & w/p). The underdrive percentage is less than 20% which still allows the engine to maintain factory specified outputs for the ancillaries. This pulley gives a 5 - 7HP gain over a standard pulley and weighs just 0.520kg (TEGIWA) Vs 2.280kg (OEM). Please note: new belts will be required to fit this product.