TAS Bivvy Bag is made of a breathable, 3-layer waterproof gammatex fabric. Gammatex is a waterproof fabric that breathes which will help to alleviate moisture build-up inside the bag. This membrane is sandwiched in between the outer and inner fabrics, which forms the basis of the 3-layer fabric. It also comes with a storage bag to protect the bivvy bag when not in use, and to make it easier to carry around.