Two layers of soft, lightweight MicroSpring Textile™ puts a soft, breathable, spongy surface next to the skin with the added benefit of a zipper which opens to allow for inspection of IV site and wound location. Loose enough to rotate. Zipper doesn’t come in contact with the skin. Sizing for Zip Tubes for Arms: Measure around the widest part of the forearm. Choose the larger size if measurement is between sizes.