Abstract: A closure system for a flexible tube, for example a sleeve, a leg or the waist of a garment. The tube has an outer surface and an inner surface. There is a cord to extend around the flexible tube, between the inner and the outer surfaces. An opening in the inner surface allows passage of a first end of the cord. A releasable anchor engages the first end of the cord. There is a fixed anchor for the other or second end of the cord. Pulling on the first end of the cord with the releasable anchor released contracts the inner surface of the tube to provide a closure or seal for the tube. The closure system provides an effective seal for a leg, sleeve or waist of a garment. The seal can be achieved simply by pulling with one hand on the first end of the cord.