I have a similar ruler with more arcs (basically parts of circles with different radii) that I got at least 10 years ago -- similar to this one:
http://smile.amazon.com/June-Tailor-...s=circle+ruler (I think JA's carries it) . I found the 28mm or 18mm rotary cutter works best when cutting the arcs (be careful not to run into the plastic as it can nick up the blade) . When sewing, remember you are in bias central with those arcs.