I had the same experience. I was using an Olfa square-up ruler for years and had several nicks in it. When I replaced it I bought a Creative Grids. I was in the middle of a quilt and my blocks were not the same measurement. I checked the rulers and they didn't match so I had to purchase another Olfa. Now I check each specialized ruler I buy against the Olfa to see if I've got to adjust the measurement.