I have a engine that the cylinders need a light cleaning
and the cross hatch reestablished. The bore is straight and true I checked it with a bore gage it's also has a .060 overbore. I would like to buy a flexhone.
What Grit and size should I get ?

I went with a 3.5", 240 grit but I haven't used it yet.

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“Buy the ticket, take the ride.”
― Hunter S. Thompson

The grit depends upon the rings you plan to use. Plain cast rings use a slightly rougher finish than moly. I don't expect you'll use chrome. Also, be sure to read the hone instructions and watch some of the Brush Research videos.

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Joshua

I plan on using just plain old cast .060 Rings.

A fine choice. And congratulations on putting the overbore decimal in the proper place!
Here's the video showing the proper use of the Flex-Hone: https://youtu.be/jgDUzOxg2MU

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Joshua