If you are looking for heavy duty or stronger mailers, have a look at our grey mailing bag and baby blue mailing bag range, which are all 60 microns in strength. 2000 lightweight but extremely professional metallic blue catalogue mailing postal bags, size 9"x12" (230mm x 310mm), with 40mm 'peel & seal' lips. Perfect for mailing catalogues and brochures through the post - fits A4 documents perfectly. Note that these are lightweight mailers and have a strength of 40 micron.