I got the 20.5" on sale. While it's great for squaring up tops and backings, it's too unwieldy for anything else. if you don't make anything larger than a 12" finished block, I would get the 12.5" ruler. While you can always use the larger ruler on smaller blocks, it is soooooo nice to have the exact size. I waited for sales and eventually got the 8.5 and 9.5.