If you follow the PCU specifications for winter clothing then this jacket will line up with Level 4 (Windbreaker) on their 7 layer system. It is lightweight, packs up into a very small size, and appears completely windproof. Here is a test for windproofness that you can do: Hold the fabric (just one layer) over your mouth and blow into it. If none of your breath penetrates the fabric, it is windproof. The way that you use this jacket is as an inside layer. One reliable person told me to wear it directly over my base layer and under my warming layer. It is very fragile so don't use it as an outside layer. Put something cotton or soft shell over it. I have tested it and found that it does a good job of trapping heat directly against my body. Don't expect to sit down somewhere with this as your only coat and be warm. You must be moving. What about sweat? Your waterproof jacket will cause sweat to build up against your body. A windproof that is too windproof will do the same. I haven't tested this aspect yet, but I believe it will be all right.
Rating:
[5 of 5 Stars!]