For quite a few years I've used Härkila Expedition socks for winter wear. Great sock Härkila but costly. I was looking to buy more of the indestructable socks from HJ Hall and i saw they do a Protrek sock Extreme ProTrekâ„¢ - Technical Walking Sock - HJ832 - Buy Online â€£ HJ Socks â€£ Official Site I ordered a couple of pairs and have used them over the last winter. Worn with a pair of liner socks I've sat out for up to 6 hours at -15 and the feet remained warm. HJ Hall protrek socks highly recomended .