I’m disappointed with a short coming here. This helmet can really do with a true medium and that’s the only thing holding me back from 5 stars. The smaller version is a little too small for me, and the large version is a little too large; but I had to go with the larger one as the smaller kept snagging on my ears. Measuring my head per the size chart said to buy the smaller size, and I was kind of bummed I lost out on some money having to return it and rebuy it. The large is also too small for my buddy’s head, so RP lost out on a sale when I tried to recommend it. I have concerns about the fit of the larger version because it still feels a little loose cinched down, but in practice the helmet has been working. I’ve had two long training rides and two races with the helmet, and I have no complaints about comfort. Visibility is great, and sound is still reasonable (a little bit of resonating noise but for an aero helmet I can’t complain). So if you’re a true medium, you’re probably a large Wing.