Designed to remove or adjusted the Flushmate Cartridge assemlby. The Flushmate wrench can be used to remove or adjust the Flushmate cartridge assembly. The wrench is designed to work with Flushmate cartridges for 1.6GPF and 1.0 GPF Flushmate models including Series 501A, 501B, 503, and 504. Located on top the Flushmate system in the center of the vessel. This is the main valve that opens and closes to deliver the water to the toilet bowl.