Blake Purely Packaging Corrugated Pocket Envelope 353x250mm Peel and Seal 300gsm Kraft (Pack 100)
Mailer Envelopes/Cardboard Envelopes - A4. 100/Pack - Rigid Mailer A4 for Book Packaging DVDs etc The Ideal Capacity Book Mailers Expand to Fit 50mm Thickness, Large Letter Size at 25mm. : Amazon.co.uk:
Postal Envelopes - The Packaging Club
100% Paper Expandable / Capacity Envelope C4 | Royal Mail Friendly