A winter midlayer, a summer belay jacket and a shoulder-season stand-alone shell all in one: The nylon ripstop Ultralight Down Shirt delivers not only our lightest-weight insulation but also the greatest comfort range. Premium 800-fill down provides a luxurious feel and pack-to-nothing compressibility. The sewn-through construction, tight channel pattern and just the right amount of down increase versatility for use in more moderate temperatures and diverse activities; wear it over a baselayer for the skin-in, then throw a shell over the top and you've got a BTU generator. The slim fit maximizes thermal efficiency, the Deluge® DWR (durable water repellent) finish sheds snow, and the simplicity complements the function, from high-output endeavors to recovery evenings in the yurt.