Chris R.wrote a review of SmartWool PhD Running Ultra Light Micro Sock on September 11, 2013
Familiarity: I've used it several times
These are probably the thinnest socks that I own. They are really comfortable and great on short runs when its hot. They look like they are breaking down faster than other merino socks that I wear. Sizing was a little on the small side for me. I wear at 11.0 and they are a little more snug than I would like. They slide down a little on runs over about 6 miles. Not sure if this would be fixed by sizing up. Overall they are pretty good.