Our classic welded polypropylene sheet protectors have become the industry standard for high quality archival preservation and presentation of artwork and documents. The weld parallel to the binding edge acts as a hinge, allowing the sheets to lie perfectly flat, making these sheets ideal for use in screwpost books. These polypropylene sheets feature superior scratch resistance to make your work look better longer, a non-stick finish to prevent adhesion to your artwork and a non-reflective finish to minimize glare. All formats are top-loading. Made of inert, unplasticized, heat resistant and chemically stable archival quality, heavy-duty .0045 polypropylene. The Polypropylene Express Sheet Protectors are available in four formats to fit Pina Zangaro portfolio books and those from most other major manufacturers. They have no liner sheet and are punched only for use in screwpost books and 3-ring binders. These sheets have passed the Photographic Activity Test (PAT) and meets all ANSI requirements for archival storage. Packed in tens in a protective metallic, resealable bag.