The ST100100 is the Sloan Flushmate 2-in-1 wrench. It is used on all Sloan Flushmate Systems. Fits tanks 500, 501, 501A, 501B, 503, 504, F31A, F3A, F3AR, F3C, F3CR, F3CC, FCE, F3ER, F31, F3G, F3G2, F3L, F3LR, F3, F3R, F3M, F3MP, F3MR, F3O, F3U, F3UR, F3Z, F32, F3K, F3KR, F3G4, F3G3, F3GR, F3K1, F3K2, F4A, F4AP, F4P, F4L, F4LR, F4N, F4B, F4C, F4K, F4KR, F4MP, F4J, F4M, F4V1, F4V2, F4V. Fits all American Standard, Briggs, Caroma, Ceralux, Eljer, Gerber, HCG Hocheng Corp, Kohler, Lamosa, Mancesa, Mansfield, Niagara, Orion, Peerless, St. Thomas, Vitra, Vitromex, Vortens, Western Pottery, Xinqi