Mylites Heavy Duty 4 mil Comic Book Silver & Golden Age Size 7-3/4" x 10-1/2" Plus 1-1/2" Flap Pack of 50 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.