I'm 5'11" and weight 134 lbs. what should...
I'm 5'11" and weight 134 lbs. what should be the right size for me?
I think for your height you've got to go medium. Might be a tad loose in the body, but I think you'll need the sleeve and body length of the medium vs the small. If you're going for a real athletic, trim, alpine fit then go small.
You do seem pretty thin... I would consider an Arc'teryx shell since they have an athletic cut. The Theta AR in a size small/medium would fit you great. If you want more room like this Patagonia will have, check out the Theta SV in a small. I'm on the same boat as you (tall and thin: 6' 130 lbs) and a small Theta SV fits me amazingly well.
I am 6' 2" 150, thin like you guys and the Medium fits me perfectly. There is enough room for medium weight layers - piton hybrid or ultralight down pullover. This piece is simply amazing. I have worn it mostly backcountry skiing but it is light enough to bring alpine rock climbing. It breathes very well for the skin up.