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