The GORE-TEX® membrane is the heart of all GORE -TEX® products. The GORE-TEX® membrane contains 9 billion microscopic pores per square inch. These pores are so small that water droplets cannot get through but water vapor can still escape. Water from the outside cannot penetrate and cold winds cannot pass through, but perspiration can escape easily, keeping you dry and comfortable all day. GORE-TEX® fabrics are created by integrating the GORE-TEX® membrane between an outer fabric and lining.