Comic Pro Line’s (CPL) OPP bags are the best plastic material available for permanent protection and storage with superior preservation characteristics. OPP Bags are 2-mil thick and made from crystal clear Oriented Polypropylene (OPP).
CPL’s OPP Bags are archival safe and recommended for long term storage. OPP bags do not breakdown, turn yellow, or off-gas like regular Polypropylene and Polyethylene comic bags.
Possesses the same characteristics as Mylar (a Polyester film), but at a more economical price, and like Mylar, CPL’s OPP Bags are naturally resistant to chemicals, oils, grease, moisture, and ultra violet rays.
https://comicproline.com/comic-pro-line/product-category/comic-book-bags/