{HEAD ~ Each} of {TAIL ~ the pair} of sensor block members is provided with an inner surface having a vertically extending recess 
of
{ HEAD ~ Each } of { TAIL ~ the pair } of sensor block members is provided with an inner surface having a vertically extending recess
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH