Blake Purely Everyday C5+ 162 x 235 mm 80 gsm Gummed Mailer High Window Envelopes (4409) 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 High Window: 45 x 90 mm, 72 up, 18 left

Zoro Tools

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