5 Star C4 Window Pocket Envelope Press Seal 100gsm 324x229mm White (Pack of 250) 5532745 Star white C4 pocket envelopes. These envelopes are made from mediumweight 100gsm paper and feature a window, allowing you to clearly display the address of your correspondent. They feature a press seal, meaning that all you have to do is apply the two glued flaps together to form an instant bond. C4 size 324x229mm Made from mediumweight 100gsm paper Window size of 40x100mm Window position 25mm in from LHS, 213mm up Press seal closure meaning that