This is a classic wedding ring design, modeled on my own band which is from Amazon (http://www.amazon.com/dp/B001AENTR6/). The scad file is parameterized, so you just have to fill in the correct value in mm. Or if you're a size 9 like me, you can just use the STL. I used the sizing from the printable Zales chart to check the quality of my print, which came out great the first try on my Printrbot Jr. (http://images.zales.com/images/popups/zales_ringsizer.pdf)