I used to use the June Taylor Shape and Cut, but it seemed that it was too flexible so my cuts weren't as straight as I hoped they'd be. Now I use the Stripology rulers. I have both sizes. I use the original one more than the squared one, since it allows me to cut more at one time. I have both sizes of the Olfa rotating mats and like them a lot. The 12" one is what I use most often. I take it to classes, even if I don't need the rotating function, because it is a convenient size.
Leslie