E. Gerber Mylites2 2 mil Mylar Comic Sleeve Bags. Each pack of Mylites2 comes with 50 comic book size protective sleeves. Mylar is also the most stable plastic, with zero off gassing. It does not absorb moisture like poly bags, and it is 100 times more resistant to the diffusion of oxygen! Use the material specified by the National Archives, the Library of Congress, and preservation experts around the world! Thanks to Mylar, the strongest plastic available with 1/3 the strength of steel, you'll get protection from: Humidity, Volatile poly bag breakdown, Acid migration, Oxygen decomposition, Insects, Ultra-violet fading, Mold and mildew as well as Oils and greases.