I'm a female and I have a fairly small head (about 21" when I measured) so I ordered this small/medium helmet. It fits quit snugly on my head, without any room to rattle around like my old helmet. The elastic strap isn't uncomfortable, and I have to say the chin strap is perfectly fine, though seems a bit short. I think I would have been better suited by a solid "medium" helmet but this one is fine, looks good, and doesn't look huge on my head. I'm a little worried that it doesn't protect the sides of my head very well but I think if I were looking for that I should have investigated different types of helmets.
Overall, fits me very well, quite comfortable, but if your head is larger than about 21" you probably want to get a bigger helmet size. If it's the same or smaller, by all means this is a terrific buy.