These pressure sensitive Archival Polyester (Melinex or equivalent) Mounting Corners virtually disappear on the page, yet hold your photos and documents firmly in place. See-thru Archival Polyester Corners simply press into place and feature a safe acrylic adhesive backing. Use to display photographs, prints, postcards, trading cards and other items. 240 corners per box. 1-3/8ths inch size.