2.89" Overall Diameter
V-Belt Belt Type
Steel

• Adapts GM alternator to original 5/8" belt
• Compatible on all Powermaster alternators, generators and most GM alternators
• Bolt hole length is .71"
• Zinc-plated for rust and corrosion prevention
• Premium steel construction

So you've converted your Flathead-powered rod over to 12 volts and bolted a GM alternator in place.
Now it's time to install the belt, but your engine pulley is 5/8" and the alternator is 1/2"!

Don’t worry, Speedway has you covered.
This alternator pulley allows the use of a 5/8" wide Flathead-style belt on GM externally regulated,
SI and one-wire alternators.