DuoDerm Signal - Hydrocolloid Heel Dressing with Border is uniquely shaped and has slits that allow the dressing to be manipulated around the curve of the heel. DuoDerm Signal gets its name from the visual indicator that shows when the dressing needs to be changed. It has a thin polyurethane film that is waterproof and protects against bacteria. The adhesive edges of the dressing are tapered, which prevents it from rolling up off the skin and helps it to conform to body contours. This wound dressing is appropriate for low to moderately exuding wounds, as well as stage I and II pressure ulcers.