Rosco's premier range of filters, Roscolux, is manufactured in a unique technology to insure the longest possible life under hot theatrical lights. Three discrete layers are combined in a tri-extrusion process. By sealing the colored layer between two microscopically thin layers of clear film, dye migration is minimized and effective life is extended. Roscolux (sold under the trade name "Supergel" overseas) is currently the most widely used filter range in the world.