I saw this helmet on GCN and the guy said that it was really good for cold weather because you can l close the vent making it aerodynamic AND keep the wind out. So I bought the helmet. I always wear a size large in every helmet I've ever owned. When I tried it on, it would not go over my head. Darn! What the heck, right? I returned it. My LBS was surprised it would not fit because he said it was actually pretty roomy. He asked, "Did you open it up?" I asked, "What"? "Did you pull the adjuster knob down"? So, there's an adjustment knob assembly at the back of the helmet that you need to pull down and open up so that you can get it on your head. Duh-oh! When I pulled it down and opened to adjustment knob, it fit like a charm. The problem in that the first time I wore it, when I went over bumps, the air vent door rattled! It sounded like something in my front end was rattling - but it was the helmet door! The good news is, it's comfortable, fits well, looks pro, and gives you a ventilation option. The bad news: it rattles when you hit a bump.