The inner cover features a specially coated Aquaguard zipper designed to repel moisture. This zipper incorporates a reverse coil to lock the coated fluid-resistant sections together. As a result, the inner foam stays dry and odor free. The inner moisture-resistant polyurethane-coated cover is made with Lycra. This remarkable material allows the cover to easily stretch and conform to the individual's shape. Without the ability to stretch, there is always the potential for surface-tension pressure to develop under the user's ischial tuberosities, which can increase the potential for tissue breakdown. The rear edge of the top cushion cover "waterfalls" over the back edge of the cushion to minimize the chance of users developing a "seam hotspot".