Window envelopes

In a window envelope the address on the letter shows through, so nothing has to be written or stuck on the envelope – handy for sending invoices and notices. College envelopes come in three sizes: E65 110×220 mm for A4 folded in three, E5 156×220 mm for a sheet folded in half, and E4 215×307 mm for unfolded A4. E65 and E5 come in packs of 1000, E4 in packs of 500 or singly.