I have both the switchback pullover and the full zip. Knot is right, they are pretty heavy wool, not so much shirt like, or layering types. I wear the pull over kind of like a sweater with a shirt underneith it. I wear the fill zip as a jacket just like Knot. I think that the full zip is a bit more form fitting. I have mediums in both and the full zip is pretty trim while I have quite a bit of room in the pull over (but not in a bad way). I just washed my pull over for the first time... threw it in the washer on cold and dried it flat. It seemed to shrink down a little, but probably just back to where it was when I first got it (Christmas) after being streached out from wearing it so much. The only way I would really call these midweight in terms of layering is that you could wear them under a shell like you would a fleese jacket. Also, they are a bit "knobby" so aren't as soft as some of the other ibex, smartwool, or icebreaker merino tops.

I do love both of my switchbacks.... would love to get some of the other colors in the pull over that Sierra Trading Post has now... but I really don't need to be spending my $$ on even more wool, especially when I am moving to Houston in 6 months....