"Great base layer in the cold, fits snug"
I have worn this while cross country skiing and hiking on the snow. Kept my core nice and warm and the zip neck was helpful as I heated up and needed to cool. If ordered in your true size it is a compression fit. Body and arms are plenty long which is huge for me as i am 6'5" and have a difficult time finding clothes that fit well in these areas. Very comfortable if you like the compression fit. I ordered another a size up and am waiting to try that as well.
"Great next2skin base layer for Extreme temps"
I have bought into the Arc's Phaze technology - it is pretty incredible at moving moisture(sweat) away from the skin. As with almost all Arc stuff, you best be athletic - because its a fit fit. I am 5'9" 170lbs - in a good way - and the Phaze medium hugs.A note on the SV - by itself, its not that burly, but once you start an aerobic activity you realize that the SV is probably overkill for anything less than deep winter temps.....