Abstract: A photographic film unit, including a film disk carried on a hub, has a mass of firm material deposited between the disk and the hub so that the mass, rather than the dimensions of the respective parts, accurately determines the relative film-to-hub alignment. The hub initially fits loosely in a central film-disk aperture. The material, a thermo-plastic, is then melted ultrasonically to flow between the disk and the hub, eliminating the looseness, and maintaining the disk on the hub in accurate alignment. According to one disclosed embodiment, the thermoplastic material adheres a retainer ring to the hub with the film disk captured therebetween. The thermoplastic then fills the interstices between the ring, the hub, and the disk to exclude foreign matter, such as processing fluids.