- TF (Twisted File) is the first and only file to employ unique and proprietary production technology that achieves unrivalled strength combined with flexibility. - TF is produced with Kerr Endodontics proprietary R-Phase Technology. - R-Phase™ thermal treatment technology optimizes the properties of NiTi files to give 70 % more flexibility and 2-3 times more resistance to cyclic fatigue than any other rotating file. **For further product information , please contact Chat support**