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