The advent of nickel-titanium (NiTi) rotary files to endodontics almost two decades ago has changed the way root canal preparations are performed, enabling more complicated root canal systems to be shaped with fewer procedural errors. Currently, a number of rotary Ni-Ti systems are available but it is difficult for dentist to decide which one is better. This book gives a detailed knowledge of various parameters, to evaluate which rotary system has superior shaping ability of the root canals as compared to other. Keeping in view the importance of parameters, each parameter has been described in details i.e. how to measure it and its significance. It also highlights the comparison of shaping ability of root canals with two rotary systems with different designs and their outcome with reasoning