The first surface 930A is exposed to the moisture donating {HEAD ~ fluid}, while the second surface {TAIL ~ 930B} is exposed to the moisture accepting fluid 
The first surface 930A is exposed to the moisture donating { HEAD ~ fluid } , while the second surface { TAIL ~ 930B } is exposed to the moisture accepting fluid
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH