250 x 350 mm mailing bags. Pack of 200. Royal Mail Large Letter size. Our grey polythene mailing bags are great value economy mailers that do not compromise on quality. Suitable for a multitude of mail order products. Popular across a wide range of industries including mailing, catalogue and internet companies. Ideal for sending 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.