{HEAD ~ The lower discharge surface} is spaced apart from {TAIL ~ the upper discharge surface} by a distance equal to D1 
{ HEAD ~ The lower discharge surface } is spaced apart from { TAIL ~ the upper discharge surface } by a distance equal to D1
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH