I think the size options are designed more for the man’s ego than his penis :D

The Magnum is only 15% wider than the regular Trojan, while the Magnum XL is 30% wider than the regular Trojan. With 6” girth, I find even the XL to be a bit tighter than ideal, but it works okay. Hell, a regular-sized condom will work for me too, I just don’t feel as much when it’s strangling my cock, and it shrinks my erection somewhat, especially the head.