I have a small foot so I was happy to find a sock liner that comes in smaller sizes.  I checked the Terramar web site to confirm appropriate size.  They don't distinguish between men's and women's shoe sizes when they convert from shoe size to sock size, but either way I wouldn't take any larger than an x-small.  My concern was that they might be too big.  On the contrary, they are tight.  Out of the package, the foot section was only about 5" long.  They do stretch of course, but they're still tight.

More importantly, I can't say that my feet were any warmer with the liners than without.  I know lots of people who swear by silk sock liners so maybe I'm doing something wrong (or maybe they're too tight!) but my feet were still freezing.