Presto Products Company Fresh-Lock thermoform zippers are engineered for processed and sliced meat packs produced on thermoform/fill/seal equipment. The zippers were designed for the demands of a variety of flexible packaging applications and is flexible, allowing it to feed smoothly into the equipment. Colored locks are available in a variety of colors to coordinate with your package graphics. Its added thickness helps ensure trouble-free performance, as the zipper is heat-sealed to the packaging film.