Castelli use the best winter membrane fabrics on the market but still find themselves wanting more breathability thats why they invented 7xair fabric for the castelli elemento 2 7xair thermo jacket they start with a fully wind and waterproof external layer and then quilt it to a fleece inner layer using the trapunto technique this results in an extremely stretchy wind resistant fabric but the stitch holes give just the right amount of air permeability and allow for a continuous exchang