The hollow cage has {HEAD ~ rows} of cross sectional holes that communicate with {TAIL ~ the ports} 
The hollow cage has { HEAD ~ rows } of cross sectional holes that communicate with { TAIL ~ the ports }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL