M-101526-F31 Sloan Flushmate Complete Replacement System for FM III 503 Series Two-Piece Toilet The M-101526-F31 Flushmate System is a complete pressure-assist flush system for 503 series tanks. It fits all porcelain manufacturers EXCEPT Kohler tank 4404 and 10” rough-in fixtures.The M-101526-F31 Flushmate System includes:Vessel-1.6 GPFLower Supply NutTank NutFlushmate-to-Tank GasketTank-to-Bowl GasketIt DOES NOT fit 10” rough-in tanks, only 12” rough-in tanks. (“Rough-in” refers to the distance from the wall to the bolts at the center of the drain.)For the Kohler K-4404 tank, see model #M-101526-F32.For 10” rough-in tanks, see model #M-101526-F33.Flushmate vessels and components do not retrofit into gravity type toilets. They are only used with Flushmate-equipped toilets.