THIS PULLEY IS THE 2 GROOVE LONG WATER PUMP SMALL BLOCK CHEVY CRANK PULLEY THAT STARTED BEING USED IN 1969 WHEN THE LONG WATER PUMP DESIGN BEGAN. IT MEASURES 6.9 INCHES IN DIAMETER AND BOLTS TO THE CRANKSHAFT WITH THE STANDARD 2.3 INCH BOLT CIRCLE. TRIPLE CHROME PLATED TOO!