330 x 480 mm grey mailing bags. Royal Mail Letter size. Pack of 200. Our polythene mailing bags are great value economy mailers that do not compromise on quality. Suitable for a multitude of mail order products. The versatile nature of our mailing bags makes them popular across a wide range of industries including mailing, catalogue and internet companies. They are ideal for sending your items through the post or via a courier. Each mailing bag has a polythene lip with an easy to use peel-and-seal strip. The polythene is 55 micron (220 gauge) thick. These bags are lightweight (enabling you to save on postage) and opaque (allowing you to safely send confidential materials).