The 555C includes the 502 universal flapper, which is long lasting, water-saving flapper and is best for use in 1.28 - 3.5+ gallon per flush toilets. It has a solid frame for ultimate reliability and will provide the best seal. The Microban® protection keeps the flapper cleaner by fighting flapper breakdown due to bacteria on the flapper itself. The 555C also includes a sealant ring, which is easy to install, by peeling the protective paper off the sealant ring and then sticking it right on top of an existing flush valve seat. It can fix a deteriorated flush valve seat without dealing with any messy glue or removing the tank with the 555C Universal PerforMAX Flush Valve Repair Kit.