The BCW Sheet Music Backing Boards are made from a full 24 point solid bleached sulfate, coated on one side with a buffered with 3% calciumcarbonate , and are precision cut to size. Fits sheet music storage sleeves. Coated on one side. Buffered with 3% calcium carbonate. Precision cut. Use with BCW Sheet Music Sleeves. Dimensions: 9 1/4 X 12 1/8 - Certified Acid Free - Independent Lab Tested