The width of {HEAD ~ the valve member} is smaller than {TAIL ~ a peripheral dimension} of the openings 
The width of { HEAD ~ the valve member } is smaller than { TAIL ~ a peripheral dimension } of the openings
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH