✔ The socks material content is 91% Acrylic, 5% Nyln, 3% Polyester, 1% Elastane.
✔ The socks are fairly color fast. I did the first wash by hand to see if they will bleed indigo blue, but they did not. The discoloration of water was minimal.
✔ The socks are fairly thick, so they may not fit into tight slippers/shoes/boots.
✔ The sizes run large. My shoe size is 7. I purchased Women 5-9. By the end of the day the sock stretches out and the sock heel is no longer in the right place. But they are so warm that I don't care where the heel is, I bought several more pairs.
The only thing I do not like about the socks is that they are shipped stapled through the sock with a plastic staple which can cause damage to the sock, which is what happened to the first pair of the socks I received.. When I attempted to issue an Amazon return for the first pair, it was marked as non-returnable item. However a chat with Amazon representative and the fact that the socks were still in original packaging got me a return label. If the Amazon return does not work for some reason, another option is to contact customer service directly at Heat Holders web site, the web site name is included on the back of the packaging.
My feet are very happy in these socks. Since my original purchase I ordered 2 more pairs. I now own black, grey, and blue. Also note that all three colors are color fast.
You can find it on Amazon by following this link.
Ali Julia review ★★★★★