This cover is especially for storing small or dust-sensitive materials. Keeps everything water-safe and organized. Designed to be used with material boxes. Easy to use thanks to the click mechanism for opening and closing. Robust, versatile, flexible, and suitable for use - everywhere: in day cares and kindergartens, in after school settings, in break rooms, and libraries. Can be used with Gratnell Trays 6254*- 6257*. Made of polypropylene plastic.