Our Single Wall cardboard boxes are great for mailing and posting. These boxes are lightweight single wall which will help keep postage costs low. Flat packed packing boxes great for posting and mailing. These cardboard boxes are perfect for mail rooms and is a packing staple; a packaging solution for eCommerce and despatch operations running on a tight budget. Flat packed for easy storage; assemble by taping flaps, standard brown cardboard colour inside and outside.