All the above sound great but I love my 4" square ruler as well and the 6" square but not sure how much 6" costs. Every so often I lose my little ruler so now have 2 of them. The lost one will eventually show up so now I do not have to spend time hunting for it when I am doing the small blocks. I like to check my sewen squares and there are times when it does not look right before sewing and no trouble to check. The kingquilt I am working on is made up entirely of
2 1/2 inch blocks and 4 1/2 inch blocks. The small ruler has been a life saver after I started using it regularly.