Sodium monofluorophosphate
Sodium monofluorophosphate, commonly abbreviated SMFP, is an inorganic fluorophosphate with the chemical formula Na2PO3F. Typical for a salt, SMFP is odourless, colourless, and water-soluble. This salt is an ingredient in some toothpastes.
Source: Wikipedia — Sodium monofluorophosphate (CC BY-SA 4.0)