Mylites 4 Magazine Mylar Sleeves 9" x 11 1/2" Plus 1 1/2" Flap At 4-Mil, these are the thickest Mylites available! Resistant to aging, decomposition, moisture, oxygen, and gas penetration. Not affected by fungus, mold, or mildew. Immune to insect and rodent attack. The fold-over flap can be tucked in or taped closed.