Quote ="-VIKINGMAN-"I would advise going a size bigger when buying oneills stuff, so in your case go for a medium.'"
Isn't 38/40 normally a medium, so if he's a 40 and you should buy a size bigger, wouldn't he need a large? I haven't got next seasons top yet but when I got this years one, I found the sizes to be pretty much similar to other manufacturers. ie, if you normally get medium then O'Neills medium should be fine. Quite a few others have said about getting the bigger size though.