TEGIWA Aluminium Crank Pulley. This K-series underdrive pulley increases performance by reducing the engine's rotating mass and by adjusting the pulley size ratio this kit offers improved acceleration, quicker throttle response. 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 0.45kg vs 1.91kg (OEM). The pulley is supplied with a brand new matching auxiliary belt for an easy install.