The S series of 6 phase alternators offers incredible output in a compact and durable package. 12 diodes, twin rectifier plates and outstanding airflow ensure long service life, even in severe conditions. The 240 amp model offers the best balance between peak output, and output at engine idle RPM. Installation Notes: This unit comes equipped with a smaller 1.75 inch diameter alternator pulley, and will require a slightly shorter drive belt for proper belt tension.