I purchased a large in this helmet because I was in-between the medium and large size helmets. My head measures 22.5" (just over 57cm) and was told that Met helmets run on the small side. Plus, if I were to wear a Headsweats underneath, I would have to have a bit of room to play with.
Upon receiving the helmet and trying it on, I noticed that there was barely any adjustment left after tightening. I though nothing of this at the time and went about wearing it. After 2 rides I noticed that I was bottomed out after tightening the helmet and making adjustments on the trail. I am not sure if the plastic straps on the retention system stretched or what happened. The helmet started to move around on my head a bit while riding, which is not a good thing. That is when I decided that the large was too large for me.
When I did ride with the helmet, I noticed that the air flows through this thing like a champ. Much better than any previous helmet I have owned. I also liked the gel pad on the forehead because it actually worked. Although it did completely block all the sweat from dripping down, it was much, much better than the fabric pads found on other helmets.
I can't really say how the overall fit was, because I feel that this helmet wasn't the right size for me. So, obviously, I cannot make a fair assessment on the fit of this helmet. I only wish I knew for sure if the medium would fit me because I did like the looks and feel of this helmet, as well as the gel pad.