Gore-Tex has sweeping uses in our society, from clothing to medical equipment. It is highly porous (approx. 9 billion holes per square inch), with microscopic openings that are 20,000 times smaller than a drop of water. This technology is the foundation for a material that is waterproof but breathable, as water vapors (a.k.a. sweat and body heat-induced moisture) are small enough to fit through the tiny pores. In outerwear, Gore-Tex membranes are attached to nylon or polyester base fabrics to create a protective shield against rain/snow, wind and cold. The Gore Company, maker of the original Gore-Tex, insists that any company using its technology must seal the seams of the garments in order to ensure that no moisture can penetrate the teeny holes made by stitching during assembly, so you can rest assured that your gear will be leak proof and sound.