These Ryman Heavy Duty Envelopes are C5-sized, 115gsm and come in a pack of 100.These envelopes are heavy weight 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. They are ideal for sending A5 documents as well as sending folded A4 documents. They are also classed as a small letter when it comes to postal charges.These C5 Ryman Heavy Duty Envelopes are a must have for any school, home or office as they can be used for a variety of everyday purposes.