View-Master Storage Sleeves Clear Plastic Storage Envelopes with Foldover Flap Choose 25 or 50 Envelopes - Your Choice Perfect for Storing and Displaying Your ViewMaster Packets and Reels They are made of cast polypropylene, 100 microns thick, with no plasticizers, acids or chlorine compounds, making them an ideal, inert material for storing photos or documents. Fun Bonus Gift with Purchase! Thanks for Looking!