Time to rethink rain jackets cycling rain jackets have until recently really been repurposed mountaineering jacketsbulky construction mountaineering fabrics insufficient breathability terrifying aerodynamics the new jacket had to be lighter more compact to fit in a pocket and more aero than ever before so castelli developed an extreme stretch version of event fabric to use on the shoulders elbows and side panels the resulting jacket fits close to the body and has minimal volume yet wi