This box features an outside box with open ends and a tray that fits inside that can easily be pushed in/out of either end. The inside box holds 2" in width and almost 6" in length and is 1" deep. The box can hold pens, shorter or sharpened pencils, Copic markers, crayons, trinkets, money, etc! This box is compatible with the 8x12 and 12x12 mats. You can find more images and a full tutorial on my blog: http://jamielanedesigns.blogspot.com/2014/05/sliding-boxes.html