This is a 48 inch wide by 16 inch mounting plate for RCV-12. It mounts over the cut out for the window on your blast cabinet. On the plate are a gasket to seal the perimeter of the film feeder and a felt liner for the unit to compress against the film. There are holes around the perimeter to fasten the plate to your cabinet.Sealant should be used on the mating surface of the cabinet and the mounting plate.