Board back envelopes are used when sending important papers or items that need protection. Manufactured from a 450gsm cardboard on the reverse and 130gsm heavy paper on the front of the envelope. Available with a printed warning, "Please do not bend" on the front of the envelope. Peel & Seal closure provides very easy, quick, and secure closure of the envelope. Home, office, school, Design room. Size 15¾" x 11, 100 envelopes per box.