All the intermediate positions between {TAIL ~ these two end positions} blocking the orifices 7 allow the loss of {HEAD ~ head} to be adjusted partially as required 
All the intermediate positions between { TAIL ~ these two end positions } blocking the orifices 7 allow the loss of { HEAD ~ head } to be adjusted partially as required
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH