The one on the right looks like a regular 5 gallon corny keg. The others look like they'd hold more, but you'd probably have to measure to see how much they hold. Or you could just use them for 5 gallon batches and just purge the extra space.
Do a thorough cleaning job. You should replace the o rings, also.
The 2 larger ones look like 10 gallon ball lock kegs. Those are hard to find and not cheap to buy. https://www.cornykeg.com/product/10-gal ... andle-keg/
The 7 Up one looks like an old style 5 gallon corny keg. U.S. built before they started getting the ones from China.
Worrying can spoil the taste of beer more then anything else! ~ Charles Papazian
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