5 Stars based on fit. I originally ordered the I/O model and immediately knew it was too big. Sent them back using Backcountry's rockin' return policy and ordered the I/OS's instead. Pulled them out of the box, placed them on my head and they were like butter. No more nose gap and a kicking field of view. The downward view field is exactly what I was "looking" for. I don't have to drop my head so much to see my feet. I also own a pair of Phenom's and they fit pretty much like the I/OS but may be a tad bigger in the nose area but both fit me pretty well.
As a reference for those wondering, I have a smaller face and wear medium sized helmets for motorcycling, etc. I think I'm around 58cm in head circumference. So if you're in that neighborhood and don't have a large noggin then these or the Phenoms will probably treat you right.
As another point if you're a male, don't think that these are just the version made for chicks. They are super sweet on your face and look killer. Just don't get the pink version or you get what you deserve.