... information 4)High quality mailing envelopes SubjectDetailsMaterialLDPE or HDPE co-extrusion material, outside-white and inside-grey color ... strong tape. This kind of bag is used for courier, express, and mail services.StylePoly mail bagThickness35-120micron ... and Different sizes are availableDetails:Durability, Multi-layer, co-extruded film provides optimum protect against moisture, puncture and tear ...