The Perfetto RoS is the one jacket that does everything well. We initially designed it as a cool-weather training and extreme-weather race piece for our pro riders, but in reality it excels in many conditions thanks to its full wind protection, great fit through stretchy fabrics, and best-in-class breathability. The current version represents the biggest performance upgrade in the four generations of this jacket. RoS in the name signifies Rain or Shine. The emphasis should be on dry-weather comfort, which is where this jacket really excels, but then you get near waterproof protection if you do get caught in the rain. We worked with Gore to develop two new Castelli exclusive GORE-TEX INFINIUM™ WINDSTOPPER® fabrics. We use a light fleece-lined water resistant version on the forward-facing surfaces and a lighter, stretchier fabric on the back that maintains the breathability of the previous fabric while improving water repellency at the same time. The Perfetto RoS is that ideal weight: no built-in insulation so you can layer over a light base layer for moderate conditions. Or you can add a thermal jersey underneath and take it to very cold conditions. You decide. The Perfetto family features are all there: excellent fit, easy-sliding YKK® zipper, long tail to protect from wheel spray, reflective panel on the back, and discreet styling that belies the jacket's racing pedigree. This is the one jacket that belongs in every cyclist's quiver.