This surprisingly thin cool weather sock is capable of the best thermal performance-to-weight ratio within a wide temperature range thanks to the magic of Primaloft polyester yarn. The development of the yarn has it's fiber origins as water-resistant, synthetic insulation. The way it is constructed into yarn creates a very low bulk when knitted, but with tiny internal air pockets that trap heat, and because the fibers don't absorb water, will also keep you dry by releasing releasing moisture and excess heat out and away from the skin. The soft yarn does have a high capacity for heat retention with the thin material, making it ideal for socks.

Specialized's designers have opted for a soft terry-loop footbed and toe, that delivers more overall comfort and more air space for thermal retention. Given that most cycling insoles are thin, and cold travels through metal screws and receiver plates that rest under the ball of the foot, that is an inevitable cold spot in a crucial zone, regardless of wearing booties or covers. You can see the overall attention to detail in the seamless toe, reinforced heel, and various directional knits to balance stretch and structure. A 7" high compressive cuff rises up to about the calf, with an effective hold to keep the sock up even while riding- which of course is desirable in cooler weather.