Most of the time x-rays of tortuous canals are used to demonstrate the capabilities of a file. This begs the question: exactly how much information do we get from an x-ray. Dr. HB Johnson, one of the pioneers of endodontics and the man who coined the term endodontics, is the person that performed the RCT of the featured x-ray taken around 1939. If we use this x-ray (courtesy of Dr. Tom McDonald, Atlanta GA) illustrating a successful end result as a benchmark, then we shouldn’t be so impressed with x-rays portrayed today as an indication of how good a file is. The files he used were carbon steel, worse than any file than most of us have ever seen. I’m including two x-rays of cases I completed soon after the introduction of NiTi rotary files. I cannot even remember which files were used, but probably not the ones I would recommend today. The point is: virtually any file can prepare virtually any canal. More difficult to illustrate is the ease, predictability, and productive capability of a file. This is why our research focuses on determining endo file limitations and efficiencies rather than endo file abilities, given the time and skill of the operator.