This site claims that "The Invisible Thin Skin Hair System is made from the lightest and most ultra thin poly ever... Each hair is placed into the transparent thin skin hair base with a new state of the art injection method...making it appear hair is growing directly from your scalp. There are no appearance of knots and the hair system looks unbelievably natural! - Ideal for swimming, sports, sleep, etc... This hair systems base takes on the exact shape of your head and almost "adheres" by itself to your skin without any adhesive tapes."
See for yourself