This movement causes {HEAD ~ the compensating spool} to reduce {TAIL ~ the opening} of one row of cross sectional holes and increase the opening of the other 
to reduce
This movement causes { HEAD ~ the compensating spool } to reduce { TAIL ~ the opening } of one row of cross sectional holes and increase the opening of the other
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH