All board envelopes are produced with a sturdy 350gsm card designed to keep your important documents from bending in the post. The peel & seal strip allows for an easy closure - no licking and sticking required! A timeless classic for any business, perfect for every day use and an affordable way of ensuring your documents are protected. Our solid board mailers range vastly in size, and we stock all the most popular sizes; C3, C4, C5, C6 and DL.