a high pressure port and {HEAD ~ a low pressure port} in fluid communication with said valve lands on opposed axial sides of {TAIL ~ said seal assembly} 
a high pressure port and { HEAD ~ a low pressure port } in fluid communication with said valve lands on opposed axial sides of { TAIL ~ said seal assembly }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL