I'd say 7below is girthy enough to need one of the wider condoms on the American market.
That said, Magnums
really aren't that big - its all in the advertising. The American assumption that they are really amuses me - and its because the USA bans larger condoms sizes:
American Condom Sizes (scroll down for table)
Magnums are 54mm, which is about average for Europe where condoms are
at least Magnum's size (and often bigger):
European Condom Sizes (scroll down for table)
Here's the scientific chart, which confirms the "average" nature of the girth of Magnums (they're designed for 5'' thick phalluses):
Condom Size VS Penis Size
Personally, I couldn't wear a Magnum, without it killing my boner, or bursting a capillary since I'm over 6'' in girth (standard-sized European condoms which are wider than Magnums have had these effects in the past, so I now look much farther afield). I've followed the measuring system on this site and now buy 69mm condoms:
My Size - your perfect sized condom (it also shows which girth sizes are banned in the USA; but are sold in Europe)
Hope this opens somebody's eyes on this site - lack of understanding of condom girths and the impact it can have upon split condoms really is a "big" safety concern!