These Ryman Polythene Mailing Envelopes measure 506x353mm and come in a pack of 5.These polythene mailing envelopes are made from extra strong opaque polythene for peace of mind when posting. They feature a peel and seal closure making them easy to use and more hygienic than standard gummed envelopes and are ultra lightweight to reduce mailing costs. These polythene mailing envelopes are tear and puncture resistant, waterproof and allow you to write directly onto them. They are also Royal Mail Pricing in Proportion approved packet sizes.These Ryman Polythene Mailing Envelopes are 100 percent recyclable and ideal for companies, retailers, students and eBay sellers who need to post items, such as clothing, that require strong packaging.