The diaphragm assembly (also called drop-in kits, gut kits, or diaphragm kits) regulates the pressure within the flushometer. When the flush valve handle or sensor is activated, the diaphragm acts as a regulator, controlling the volume of the flush and maintaining the necessary pressure within the valve to prevent water from flowing when it is off.
If you are looking for the individual parts; molded discs, diaphragms, guide assemblies, relief vales, refill heads or flow rings we have those too and in stock for same day shipping.
VMS stocks both urinal and closet kits from gallons per flush (GPF) ranging from .13 urinals to 4.5 GPF closet bowls.  We stock both Junior Kits, to include the diaphragm only, to Senior Kits, which will completely rebuild the entire flushometer in both natural and synthetic rubber components.  VMS has the diaphragm kits you need in stock and ready to ship that same day from the brands you trust; American Standard, Delany, Kohler, Moen Sloan, Zurn and others.