These peel seal strip catalog envelopes are made of 28 lb pond paper, making them sturdy enough for unfolded documents, catalogs or magazines. Peel-seal adhesive strip, self-sealing closure eliminates moisture, protecting contents and speeding packing. Center-seam construction with square flap allows you to remove strip for a clean, quick seal upon contact. Provides a clean professional appearance and consistent sealing. Keep contents safe and secure.