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. The 170 amp unit comes equipped with an OEM diameter pulley, making it perfect for high RPM and racing use. THIS UNIT COMES SELF EXCITING IT HAS NO PLUG AND NEEDS NO CONTROL HARNESS. . . GREAT FOR LS ENGINE BUILD APPLICATION USING GM TRUCK STYLE MOUNTING BRACKETS!