Clear Mailing Bags A4 Plus size 230mm x 305mm 9" x 12" + Lip, 100% Recyclable Our Clear mailing bags are manufactured to high tolerances and that gives the bags strength. We also make them thicker than our competitors, The thickness of the film is 38 mu, All of our Plastic postage bags are made from Strong Polythene, They have a permanent Peel and seal closure with high tear resistance. How to find the correct bag for the items you are dispatching, firstly lay out your item and measure the long and short dimensions of it, and then check the sizes quoted in the Heading above are close to the size you need , The sizes quoted don’t include the flap.