Rating: 5 / 5
While I couldn't find a fabric weight on Patagonia's website, I think this is the lightest weight wool base layer I own. (I also have tops from Ibex and MEC and Skin 200 Leggings from Icebreaker.) Also a somewhat looser weave. Great fit (size XL) on a tall, lanky guy with very long arms, and it's long enough so that the shirttail never pulls out in the back. Absolutely remarkable insulating capability and totally breathable, from -10 (under a sweater and parka) to +70 F (on its own); works as well as synthetics weighing twice as much, and doesn't stink. As I am cold-prone I especially like turtlenecks in the winter. I do get a static charge the first time I put the shirt on after a washing but not otherwise. After a good season's use it looks like new. I like this turtleneck so much that I bought two more.
UPDATE: Patagonia now lists the weights of its wool products, and Wool 2 comes in at 111g/m2, twenty per cent lighter than Icebreaker's lightest weight.