BOARD BACKED ENVELOPES: These rigid mailers are designed to contain unfolded paper - they're perfect for posting & storing certificates, legal documents, passports, ID cards, photos, artwork, gift cards, currency, etc. You can count on these envelopes to provide the protection your important documents need as the rigid board back protects against bending and creasing. PRINTED DO NOT BEND: Strong 120gsm brown kraft paper (front) & board (back) construction offers full on protection & rigidity to keep contents flat, crease-free & safe. "Please do not bend" is printed in large red font on the front to caution all handlers, great for the post and mailing. SECURE & EASY TO USE: Each envelope has a built-in peel & seal strip which reduces packing time & cost by providing a strong & hassle-free seal. The envelopes offer extended shelf-life over self seal envelopes - just remove the strip & press the flap down to seal! SIZE DIMENSIONS:C5/A5 229mm x 162mm - Select the number of envelopes