Got this jacket for Christmas and decided it's time to write a review. This jacket is an excellent mid layer and good outer layer down to mid 30's depending on the base layer you wear underneath. I am 5'11" 185 lbs and the large fits how it is suppose to (snug but not skin tight). I have a 43/44 inch chest and its a little snug in the shoulders. However I prefer this rather than have it be bulky around the torso. Plus, it does not inhibit motion in any sort of way due to the stretch fleece side panels.
It fits as a mid layer under every hard shell and soft shell jacket I own with ease (my purpose for asking for this jacket). As far as the materials they are quality MH materials that I would expect in this price range. Even with knowing the weight, I was still shocked when I first put it on at how light weight it actually was. So while it does not feel like much, the thermic insulation does an excellent job of trapping heat without bulk. I wear a smart wool base layer, the zonal, and my north face bionic and am good down into single digits no problem even with wind. I would not say the zonal itself is windproof but wind resistent (except for side panels which are not) and it is water resistent.
One note on breathability, I wore it while shoveling snow under a hard shell with a polertec power dry base layer and the outside of the zonal was soaked while the inside was pretty dry. My hard shell is not very breathable (north face resolve) so all the moisture was trapped between the two layers but the mh kept me warm even after I stopped to take a break staying outside. After I went inside and took it off it dried completely in about a half hour to 45 minutes, def would have been even quicker had I kept it on...