{HEAD ~ the valve seat} further comprising {TAIL ~ a generally flat diaphragm engaging surface} having a second surface area, the second surface area being less than the first surface area 
comprising
{ HEAD ~ the valve seat } further comprising { TAIL ~ a generally flat diaphragm engaging surface } having a second surface area , the second surface area being less than the first surface area
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH