The Velocity is fully seam sealed with a Z-Lining membrane that is waterproof and breathable and has a 10,000mm/8,000g DuPont™ Tefl on® finish. It also has an Outlast® fl eece/tricot lining that will regulate your temperature. Detachable lining system zipper allows you to zip in the Yamaha liner (sold seperately) for extra added warmth.