I bought this set square to me months ago just 3. During lectures of my studies I use it regularly, and of course a lot, so I'm more disappointed that I had to find that after a very short time to wish the dimensional accuracy leaves something. By that I mean the "long line" that has long ceased being "straight" with me, but almost hunchbacked. Regularly are small remnants of the plastic on the paper. Perfectly straight lines can no longer be distinguished, I will have to look good for a new ...