Mapac Archival portfolio sleeves are acid free will prevent your precious artworks discolouring over time. These sleeves are made of a heavy gauge 190 micron polypropylene material. They have welded holes and double welded spines for strength. They are coated with a special glare reducing finish to allow easy viewing in all lights. The sheets are non-stick and can be turned without effort like pages in a book. These Mapac sleeves lie pleasingly flat even when filled with artwork.