The S series of 6 phase alternators offers incredible output in a compact and durable package. Highly efficient, these units use less horsepower than conventional 3 phase alternators. 12 diodes, twin rectifier plates and outstanding airflow ensure long service life, even in severe conditions. Installation Notes: This unit comes equipped with a smaller 1.75 inch diameter alternator pulley, and may require a slightly shorter drive belt for proper belt tension.