The Opus tiles are 10.5 inches square and made from the same Fabriano paper as the 3.5" tiles. Nice to work with - different feel with the Prismacolor pencils. This is not a favorite piece for me - I struggled with it from the start. However, I was not going to give up. I kept working it and finally added color to make a tile that at least was okay in my eyes. The photo does not show the color clearly - some of it is just lighter. Since I didn't really like the way it was going, I used it as an exercise to work with blending color pencils as that is still something I am learning and in this one used a blending pencil instead of mineral spirits with Prismacolor pencls. I wanted to share the finished ZIA as a commitment to not giving up.