I use my 6X24 a lot because it will cut the whole distance across the width of the fabric (selvage to fold). I really like my 15X15 square to square up blocks and square the corners of my quilt before binding. For seeing clearly, I am partial to Omnigrid rulers. I have used the same Olfa 18X22? green cutting mat for 15yrs or more. I am now using the back side to cut on because I do finally have some divots in the front surface. Like most quilters, I have a slew of others size rulers that I have purchased for different projects.