I want to put a water filter on a spout that is 5/8 inch.
That is apparently a very odd size and I haven't been able to find an adapter to the water filter, which is the std 55/64" size.
Any suggestions where I can find one? I checked my local home depot and 2 plumbing supply places near my house, so I think I need to go on line.

Also, the faucet manufacturer told me the dimension is "5/8 - 27 UNS" What do the extra letters mean, and is that important in purchasing the adapter.

Thank!