So far, I have used these sox for cold weather/cold water kayaking, and kayaking associated activities.  I wear them next to my skin and under a pair of 7mm neoprene dive booties and a 7mm "Farmer John" suit.  I have kayaked for hours and have not experienced either cold or wet feet.  Additionally, I have stood in 33 degree water exceeding the height of these sox for over an hour, and have been neither cold nor wet (with the aforementioned booties and suit, and with patches of floating lake ice).  The quality of construction is impressive.  I was reluctant to spend the money on these pricey items, but now I feel it was money very well spent.  I own many NRS products and have never been let down.  Bravo!, and thank you to the folks at NRS!