{HEAD ~ The undersurface} of the top portion 21 of the valve member 20 forms {TAIL ~ another sealing surface} 40 for selectively substantially preventing fluid flow through the opening 28 
forms
{ HEAD ~ The undersurface } of the top portion 21 of the valve member 20 forms { TAIL ~ another sealing surface } 40 for selectively substantially preventing fluid flow through the opening 28
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH