The Twisted File (TF) combines 3 proprietary processes to deliver optimal strength and flexibility: 1. R-Phase heat treatment technology is used to increase file flexibility and resistance to cyclic fatigue. 2. Twisted design, not ground: Twisting helps preserve grain structure and reduces formation of microfractures. 3. Strength and flexibility: Twisted files can withstand approximately 60% more torque. Twisted Files are up to 70% more flexible than the other NiTi files.