Brodart's Fold-On archival book jacket covers are acid-free, chemically inert and will not yellow of crack with age. They are made with super-clear polyester mylar with acid-free, non-printed paper backing. The PVA adhesive is pH neutral. These are center-loading covers which can fold down for a custom fit. This Popular Pack includes ten (10) 8 1/2" x 18 1/2" sheets, ten (10) 9 1/2" x 20" sheets, and ten (10) 10" x 21" sheets.