Blake Purely Everyday C4 229 x 324 mm 100 gsm Gummed Mailer Window Envelopes (2710) Manilla Pack of 250

Amazon

Gummed flap for a long shelf life and reliable sealing High quality 100 gsm paper Mailing wallets perfect for use on mailing and inserting machines Ideal for business correspondance, letters and other mail Window: 40 x 105 mm, 24up x 213 left

Zoro Tools

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