Bilt Osmotic Scale Reduction (O.Sca.R) Cloth Pack/Limescale Inhibitor - small (D107) Helps reduce limescale in your espresso machine by converting the calcium and magnesium ions into low level sodium ions. For 1 - 2 liter reservoirs. Operates between 5 and 40 degrees celsius water temperature. Meets FDA requirements (Heading 21, Section 173.25, par. A. Sub 1). Manufacturer recommends to replace once a year.