11×13.5″ Cardboard Stay Flat Shipping Envelope

Made from 28PT coated cardboard with a kraft back, these rigid mailers measure 11 by 13.5″ and have a stay-flat design that helps protect documents, photos, and prints from bending during shipping. The self-adhesive strip provides a secure seal without needing extra tape, and the heavy-duty construction adds a layer of protection for flat items like certificates, artwork, and promotional materials. The coated front offers a smooth surface for labeling or writing, while the kraft back gives the envelope a sturdy feel. Suitable for mailing important papers, presentations, or anything you want to keep flat and undamaged.