Blake Purely Everyday C5+ 162 x 235 mm 80 gsm Gummed Mailer Window Envelopes (4406) Manilla Pack of 500

Amazon

Gummed flap for a long shelf life and reliable sealing High quality 80 gsm paper Mailing wallets perfect for use on mailing and inserting machines Ideal for business correspondance, letters and other mail Window: 45 x 90mm, 60 up, 20 left

Zoro Tools

A vast range of sizes and window variations available, with trapezium flaps and outside seams, suitable for all machine inserting.