Aquacel - Non Adhesive Foam Wound Dressing has a film backing that makes it waterproof and blocks out bacteria. This backing also allows excess moisture to evaporate, preventing maceration. The absorbent pad is comfortable against skin and contours to the wound bed. Because this primary dressing does not have an adhesive border, it will need to be held in place with medical tape or a secondary dressing. This Aquacel dressing measures 4" x 4".