THIS IS A TRIPLE GROOVE CRANKSHAFT PULLEY FOR SHORT WATER PUMP SMALL BLOCK CHEVYS. IT HAS THE STANDARD BOLT PATTERN TO MOUNT ON ANY PRE 69 CHEVY BALANCER. IT IS NOT IDENTICAL TO THE 3 GROOVE PULLEYS USED FROM 1955 TO 1968, AS THE 3RD PULLEY IS THE SAME SIZE AND MODIFIED TO BE MORE ROUNDED ON THE FACE - FOR SHOW APPEARANCE THIS IS MADE OF HIGH QUALITY STEEL AND THEN SHOW QUALITY CHROMED. THE SIZE IS 7.3 INCHES IN DIAMETER, JUST AS THE FACTORY USED.