It has something they call ‘Core Vents’ which are for additional ventilation, allowing air to move into the jacket. They are placed up front in the jacket for maximum air input, and to keep them out of the way of pack straps. They are somewhat in place of the usual pit zips that most jackets incorporate for ventilation. Although this was a nice feature, I would have still liked the pits zips when you really want to cool off, that is a feature I have always liked in a jacket and was a big downfall on this jacket.
I also got the optional hood, which clips on easily with Velcro. It is a nice addition to a great jacket and keeps your head dry and keeps those annoying drips from working there way down your neck. The hood fits snugly and fits nicely under a helmet. The fact that the hood is optional was a bit odd to me, it is an important piece of the jacket for a mountain biker, and I consider it essential.
Therefore, how did it perform? I had it out in a couple of snowstorms, and the waterproofness was perfect, but the best part was how well it breathed. The temperatures were warm enough that I built up a good amount of heat and sweat going up to my usual singletrack, and I never noticed any more dampness than I usually get while riding. When I switched to go downhill, the jacket kept me warm, and it was very wind resistant, preventing the sort of wind chill that likes to creep into the torso when moving along at a good clip. On another day it was bone chilling weather. It was extremely cold, and windy with an occasional snow flake, good weather for a polar bear or a nutty mountain biker. The jacket did a great job protecting me from the elements.
The jacket did fine in my shower test and kept me dry for the brief time I was testing it. It was not quite like riding in a full rainstorm nor a long drizzly ride, but it still showed that it was good and waterproof. I also had my daughter spray me with a hose while I was on the bike with the jacket and hood on, she enjoyed that immensely drenching me as much as possible. The jacket did just fine with the hose test, and I had no damp spots anywhere under the jacket.