Great cold weather option
Great sock for cold weather activities. Have used one pair on multi-day trips to fly fish in the Fall/Winter. Outstanding option beneath waders for extended periods in the water. Stays put, does not bunch (make sure you get the right size) and durable. These socks have replaced Patagonia Expedition socks and Sierra Primeloft booties.
Negatives: weight/size and drying time. When wet or damp they are tough to get thoroughly dry even in the foot box of a down bag.
Overall, outstanding albeit pricey option for cold feet. When the day can be made by staying warm, this is a great option.