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