I have a 12.5 square but frankly, use it very little. I usually just use my 6.5 x 24" to square most of blocks. I find when the rulers are different manufacturer's during the initial cutting and then trimming process, things have a tendency to be a bit 'off'. I try to use the same brand ruler throughout my quilt. I don't know that I'd want to keep track of that many square rulers when the big one will do all the smaller measurements. I find my rotating mat to be most helpful during the trimming/squaring process.