The annular protrusion is symmetrical about the orifice and has a proximal end affixed to {HEAD ~ the valve body} with {TAIL ~ an inwardly directed extension} which provides a sealing edge 
with
The annular protrusion is symmetrical about the orifice and has a proximal end affixed to { HEAD ~ the valve body } with { TAIL ~ an inwardly directed extension } which provides a sealing edge
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH