Mefix consists of an apertured, non-woven polyester fabric coated with a layer of an acrylic adhesive, and protected on the roll by a release paper backing. The apertured structure imparts a degree of lateral extensibility and conformability to the product, which has a high tensile strength and must be cut with scissors. Mefix is available in a range of widths and is sometimes referred to as a `dressing retention sheet'. Because the tape is permeable to water vapour, it is unlikely to cause tissue maceration or be adversely affected by sweating. As both the fabric and the adhesive mass are radio-transparent, Mefix does not have to be removed if the patient is to be X-rayed.