haven't see that particular ruler...but
it looks like a triangle ruler with the top cut off. Looking at the utube instructions the largest side appears to be 5" wide and fits on a 2 1/2" jelly roll fabric.
Hmmmmm....got a triangle ruler?
Oh WAIT!!! Kaye Woods did that with her triangle rulers BUT folded the fabric in half first.
http://www.youtube.com/watch?v=OXYiTYj_crg Don't want to mess with inset seams...cut the full hex in half