{HEAD ~ a valve body} defining a main valve cavity and {TAIL ~ a smaller diameter metering valve cavity}, with a narrow interconnecting passage between them, 
defining
{ HEAD ~ a valve body } defining a main valve cavity and { TAIL ~ a smaller diameter metering valve cavity } , with a narrow interconnecting passage between them ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH