Heavy Duty Envelopes are available in both C4 size and 16"x12" size for that extra room, weight 115gsm to ensure documents are safe during postal transport and have a peel and seal closure making them easy to use and more hygienic than standard gummed envelopes. Ideal for sending A4 documents which you would rather not fold. Great for storing patterns and designs. A must for home, office, school, design room, tailoring. 250 envelopes per box, available in two sizes.