Pack of 250 B4 Self Seal 90gsm Manilla Pocket Envelopes. These envelopes are made of quality 90gsm paper and feature an easy to use self-seal adhesive flap. Just insert your letter, fold the flap open and press down to seal, there's no gum and no licking required. These envelopes are B4 size, measuring 353 x 250mm, and are ideal for non-standard format paper. This pack contains 250 manilla envelopes.