Spanner wrench for all pre-2012 EWS under counter and counter top sink filtration systems. For all model #s starting with the following letters: FUGAC, UU, FU, and RU. Assists with filter replacement and easily opens the filter housings. [note color=#fde891]New EWS under counter filtration systems do NOT require a spanner wrench. Model #s that do not require a spanner wrench: DWS, DWS-UV, RO3, RO3-UV, and SS.[/note]