The body of the Tempest Rain bootie is constructed from three panels of Capo's RainE fabric. RainE is 100% water resistance polyurethane coated membrane with exceptional stretch featuring a micro fleece insulation back. Three panel construction (two for the body and one for the heel) is used for proper anatomic fit. Nothing worse than an ill-fitting shoe cover. Especially one that is designed to keep your feet dry. Capo uses their Bock System for the zipper. This proprietary zip stop technology applied to the shoe covers to bolster and maintain seam strength and heal cup integrity.