Great warmth when used in a sleeping bag and tent overnight in the Arctic. Tested down to -20 deg C without additional socks/layers. Very comfortable and although not particularly robust and best suited to tent use, the Rab VB socks can be popped over the top to provide waterproofness when popping outside for a short time in the snow.
They are very light weight and compact down into their own tinny bag, very warm. Perfect inside the tent and sleeping bag.
Roasty, toasty, and beautifully soft. Just right for my cold feet, both @ 8000m AND relaxing at home. Brill!