These are made in Paper by Fifty-Three, references from a book I've been meaning to use for 3 years. I upgraded to get the watercolor tool, which acts like the thin, unsized paper I use for Chinese Brush painting. Didn't get the color mixer because you can layer the watercolor. Didn't seem that useful. It's the only app I've paid for to date, the only one I've been 100% satisfied with (does everything I want it to do.) Oh no, what will become of my sketchbook goals?