A primary issue that so many riders have with light, weatherproof riding shells is that they develop a clammy, humid feeling once you start sweating, as many of them are poorly ventilated. Not so with the Assos sJ. blitzFeder Men's Jacket. The world-renowned fabric fanatics at Assos developed the blitzFeder's Foil043 fabric to combat this precise complaint. It's feathery light, at a claimed 96g for a size Medium shell. It's ultra-thin, too -- ball it up into the integrated stuff sack and it easily fits in a jersey pocket. Assos calls the material a "natural windbreaker," which is its way of saying that there's no membrane applied in creating the windproof qualities of the material; the structure of the threads and the density of the weave make it so. A treatment is added to give the fabric water repellency. The fabric also pulls off the incredible trick of being resistant to flapping in the wind. If we could explain how it does this -- or if the designers would share this closely-guarded information with the public so that we could -- we would. As with most Assos apparel, it's designed for a snug fit, and it fits best when in the riding position. There is elastic at the wrists and waist to keep things in place, and there are elastic mesh inserts on the sides of the back and under the arms to allow some stretch. Finally, there are reflective tabs on the shoulders and on either side of the waist. The Assos sJ. blitzFeder Men's Jacket is available in a translucent color called White Panther. Sizes run from X-Small to the largest called TIR.