Blake Purely Everyday DL+ 121 x 235 mm 80 gsm Gummed Mailer Window Envelopes (1114) Manilla Pack of 1000

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 90 mm, 18 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.