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