When two become one take two of castelli39s best technologies and combine them in one jacket we think you39ll find a jacket that now offers a new standard in balancing light weight stretch breathability and warmth in 2013 castelli developed the 7xair fabrica proprietary windproof fabric that provides seven times the air permeability of existing membrane fabrics in 2014 they then invented the alpha jacket with a number of innovative construction techniques to revolutionize the perf