T90P Poly Sure Opaque Poly Mailers measure 830mm x 1050mm. They are produced using co-extrusion which makes them extra strong and lightweight. Our poly mailers are also waterproof, tear and puncture resistant, so they can reduce your returns due to transit damage, while adding almost nothing to your postal costs. These environmentally-friendly envelopes are made from fully recyclable and degradable 45 micron polythene, with all print in water based inks. Because of their opaque finish, heat sealed edges and tamper proof seals, the envelopes cannot be seen through or opened without leaving evidence.