If they are off they can be corrected if you’re careful and take your time. But you’re much better off paying a bit more and getting something you know you can trust. This is one of the few tools that I’d only buy direct rather than from the internet as I’d want to verify that it’s truly square before I parted with my cash. If you know your square is well, square then you can save money further down the line for years to come. I’m not saying don’t buy these but make sure you can return them if they ain’t square.