5-mil, polyethylene protection Crystal clear gloss finish; protects from moisture, smudges, dirt and grime Rounded corner design reduces lifting and keeps edges from curling Acrylic adhesive adheres permanently Acid-Free, will not crack or yellow with age Our Poly-Shield Label Protectors stretch and conform to book spines, and provide 5-mil polyethylene protection of all your labels. Protect your labels from moisture, smudges, dirt and grime. The rounded corner design reduces lifting and keeps edges from curling. The acrylic adhesive adheres permanently. Acid-Free and will not crack or yellow with age.