I bought the Guidelines rulers, the two 6"x12" ones that you can snap together to make a 6"x24" or a 12"x12". That part is neat, having those size options.
However, I found that the rulers produced a lot of glare, especially under fluorescent lights. I took them to a class and was unable to see the markings because of the glare. I ended up putting them away and borrowing a ruler from someone else, and I haven't used them since.
If there was some way to reduce the glare, I think they would work very well. But now I'm sorry I paid so much for something I won't use.
Hope this helps you.