All this information is so helpful! I have a self healing Olfa mat that is not beat up, no nicks or gouges. So, I've another question related.....how can the mat affect the cut? Mine seems to be in good shape, but to be honest, I never considered that as a possibility. I'm relatively new to quilting, just two years or so. So while I've learned tons from threads, videos, and trial and error, I still have so much to learn! I've seen the stripology rulers, and I'm intrigued....are they really that accurate? I would think all those slits in the ruler would make them more likely to shift when cutting.