K3 XF NiTi Files – 25 mm, 0.40/0.04, 6/Pkg. K3 XF are rotary nickel titanium files providing clinicians with the safety and self-centering features of the original K3 plus a new level of flexibility and resistance to cyclic R-Phase Technology. K3XF is the ultimate in safety, flexibility and control for rotary file users looking for a stronger and more flexible file.