I size up one for boys swim.

The 2 pc rashguards are closer to a 3/4 sleeve depending on if you size up, I size up for Oak and they’re full length, if you prefer a more snug fit normal size is more of a 3/4 length. If you got our swim last year it fits the same! We did modify the string length on the trunks to be much shorter but that was the only adjustment!