I need to replace sink faucet, bought a Moen.
But it appears I have a weird setup and need adapter.
As best I can measure the OD of the threads under the sink is 0.790”
The ID of the Moen connection is 0.520”, which equates to 3/8"?

Am I better off replacing the valves with a “standard “ male fitting?
All the faucets seem to have female fitting for the water.

If you can take the one or the ones you need to connect over to your local hardware store or big box store and you will find several different connections. There are washing machine connections, dishwasher connections, sink connections, garden hose type connections, and some with different combinations on either end and that's what you probably have and dealing with?

Edit: Forgot about refrigerator connections for ice makers too.

Home depot usually has 2 different size water lines with various lengths. Like A12 said, take your old one to the store with you so you get the correct length as well.

But yes, that water valve looks strange and looks like a permanent connection from the valve to the water line. How is that valve connected to the water line at the wall? If they unscrew, I would change the valves.

Plumbing in or out = flow, so the ID is used for plumbing, not the OD.

Are you sure you don't need to just get a male/male threaded coupling to connect the two? Faucet connectors are pretty standard size.

I just bought a Moen faucet for our kitchen. It says somewhere on the box or directions what size connector it is.

Follow-up for anyone that have have similar issue.
Amazon to the rescue, 1/2” - 3/8” compression coupler