The 100 Half Back Current (Modern) 24pt Acid Free Backing Boards 675HB by E. Gerber is the highest quality backing board available for preserving your collectibles. Made from 100% acid-free 24 mil thick cardboard, these backing boards provide extra rigidity and protection. They are produced with a 3% alkaline buffer throughout and maintain a pH level of 8.0+ to ensure the preservation of your collectibles. These boards meet strict U.S. Government standards for archival storage and are designed to protect your collectibles from the effects of aging. With a size of 6-3/4 X 10-1/2, this pack of 100 backing boards is perfect for storing and preserving your valuable items.