These mats are cut from Crescent, Bainbridge and Artique matboard. You will receive a variety of beautiful colors. Mats would be great for artist or school art work projects, perfect for your photos, prints or original art. We can also do custom orders. Just let us know what you are looking for and we will get back to you with a quote. Actual opening size is 3 15/16" 5 15/16"