Band-masks generally have a single faceplate, which may be relatively large, firmly mounted to a rigid frame which also holds the demand valve or other gas supply components. The frame may be of metal (often brass), a strong engineering plastic, or a fibre reinforced resin composite. A face seal and in some cases a neoprene hood is clamped on by the metal band, which may have several buttons protruding, onto which the straps of the spider are fastened to secure the mask to the diver's head. Where a hood is included, it may have a zipper up the back for ease of fitting, and the spider is secured over the hood. A band mask is generally heavier and more cumbersome to fit than a soft skirted mask, and is not as easily fitted without assistance. It provides greater security and protection to the diver than a soft-skirted full-face mask, and is lighter and quicker to fit than a helmet.