Sorry to hear you were so frustrated with the inaccurate 60 degree triangle rulers. I have used the Clearview brand EXCLUSIVELY and EXTENSIVELY in the last 20 years and never encountered a problem with them. On the other hand, I have a little tool I sell and sometimes the screen isn't aligned correctly when it is printed. I have to reject those from the manufacturer. They should each be checked and rejected if it is not printed within their tolerance for error. Some companies have a bigger tolerance.