{HEAD ~ The flow field plates} are {TAIL ~ an assembly} of a cathode side unipolar plate and an anode side unipolar plate 
{ HEAD ~ The flow field plates } are { TAIL ~ an assembly } of a cathode side unipolar plate and an anode side unipolar plate
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH