E. Gerber Full-Backs 'Standard' 42-Mil Backing Boards & Mylites 2 'Standard' 2-Mil Comic Book Mylar Sleeves - 50 of Each! Full-Backs: These are the highest quality boards found anywhere! At 42-Mil, these are twice as thick as regular backing boards! Made from 100% acid-free, virgin wood, cellular fiber, 42 mil. thick cardboard. Contains a 3% alkaline buffer and a pH content of 8.0-8.5. Sold in packs of 50. Measures 7" x 10-1/2". Mylites 2: At 2-Mil, these are the twice as thick as regular Mylites! 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. Sold in packs of 50. Measures 7-1/4" x 10-1/2" Plus 1-1/2" Fold-over Flap. Includes two packages: 1 pack of 50 Full-Backs 'Standard' & 1 pack of 50 Mylites 2 'Standard'.