I purchased these socks with an eye to the natural fibres. The silk fabric is soft to the touch and yet incredibly durable for such a fine knit. I found my feet stayed warm and dry all day long. Since I have neuropathy in my feet, this was a crucial plus for me. My feet get painfully cold very easily, and then are very hard to warm again. The reason for the 4 Star rating is I find the cuff is too snug when pulled to full length. I fold the sock cuff over to the ankle in order to keep it from cutting off the circulation to my feet which in turn causes them to become cold ... a true viscous circle! I am watching for Black to be back in stock so that I can order several more pairs. Please keep these in stock year round. I would also order more pairs of the cozy Bleu Foret alpaca ankle socks. They keep my feet toasty warm on cold nights. Soft and natural fibre is used in the alpaca socks also.