Looking for the superior clarity of polyester in a sheet that will lie flat in a screwpost book? Look no further than our new Flex-Hinge Polyester Sheet Protectors. These top-and-bottom loading 100% archival sheets are much clearer than polypropylene sheets and they lie perfectly flat thanks to a hinged binding edge. Available in eight formats and sold in packs of ten. Made of archival grade DuPont polyester (polyethylene terephthalate), these sheets have high transparency and tensile strength, are non-yellowing at ambient temperatures, are chemically and dimensionally stable and are resistant to most chemicals, moisture and abrasion. A non-stick finish prevents adhesion to your artwork. Approved by the Library of Congress for archival storage. Lined with 10 pt. black acid-free and lignin-free paper. Both plastic and paper pass the Photographic Activity Test (PAT) and meet all ANSI requirements for archival storage. Packed in tens in a protective metallic, resealable bag.