{HEAD ~ An annular recess} is formed in an outer surface of {TAIL ~ the orifice ring} and has first and second axially spaced walls 
{ HEAD ~ An annular recess } is formed in an outer surface of { TAIL ~ the orifice ring } and has first and second axially spaced walls
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH