"Very thin, light insulation that works well with a liner sock."
These socks are ideal for use with liner socks inside a well insulated boot or in warmer weather. They insulate surprisingly well for their ultra-light weight and thickness. They also wick well. They have a smooth, tight weave that allows them to slide with ease between a liner and the inside surfaces of a boot, so they help minimize hotspots and blisters. I use these for cycling and have had them down to low single digits (Fahrenheit) in complete comfort, but, again, inside well insulated riding boots.