The Self Adjusting File (SAF) is the only representative among endodontic files which enables preparation of the surface of a tooth with irrigation. Nickel‑titanium alloy in the form of a grid allows to adjust the flexible file to the canal wall and expand according to its three‑dimensional anatomy. Simultaneous rinsing increases the efficacy of cleaning. Unlike most of the available systems endodontic rotary motion was replaced by movement in the vertical axis. The cutting blade characteristic for conical cores turned into an abrasive surface. The combination of in and out movements with the abrasive surface resembles the effect of sandpaper. The first part of the paper takes into account the description of The Self Adjusting File and its the manner of operation while the second is a description of its characteristics in the clinical aspect.

Key words: The Self Adjusting File, anatomical instrument, chemo‑mechanical root canal space preparation.