-Nickel-titanium NiTi tools are much more flexible suitable for the curved and narrow canals which, have a better cutting capacity, they have a shape memory (always return to their original shape).
-Manual files NiTi type K (Kerr) best for finding canals and working the thin root canals.
-With a tightly twisted steel spiral, four cutting edges (the low ability of cutting), flexible – provide safety.
-Low ability to transport outside the cut dentin.
-Files can be re-sterilized in a steam autoclave at 134 degrees C