Craft designed their Pro Zero Extreme fabric for extreme intensity riding in cold weather. And while these base layers are not meant to be limited to extreme weather conditions, we have found them to be cozier than most cycling specific base layers. We've used them in long and short sleeved versions, and found them to fill our needs across a wide range of temperatures from 25-55 degrees Fahrenheit. We have them both here in our Pro Zero Extreme Base Layer Women's Combo Pack. With the pair, you'll be armed and ready to battle the elements this winter.Craft Pro Zero Extreme was first designed for the Swedish Nationall Nordic Skiing team. In the early and late season, they often skied in cool conditions where they were generating enormous body heat through intense efforts. They needed a base layer that would trap in warmth when they were skiing at a moderate pace, but that could wick and vent like mad when their effort level was pegged. Hence, Pro Zero Extreme was born.Pro Zero Extreme is built with hexachannel Pro Cool fabric against your skin, identical to what you get in a summer weight Pro Cool base layer. This hexachannel layer is paired with Craft's hollow-channeled Thermolite fabric to help trap in body heat on cool days -- two layers into one for ultimate performance. Both versions have a seamless torso design, so a tight-fitting jersey won't cause your base layer to chew into your skin. Adding to the comfort is the fact that Craft uses what they call 3D cutting lines. You won't see any straight seams on the Pro Zero Extreme base layers. The panels and seams are curved identically to the shape of a cyclist reaching for the handlebars.The Craft Pro Zero Extreme Women's Base Layer Combo Pack is available in Black or White in sizes X-Small through Large. The pack includes a long sleeved and a short sleeved base layer.