{HEAD ~ A pair} of right and left main pipes and or {TAIL ~ a pair} of right and left down tubes, or a main pipe and a down tube are formed of one piece of continuous pipe material with its intermediate portion warped 
{ HEAD ~ A pair } of right and left main pipes and or { TAIL ~ a pair } of right and left down tubes , or a main pipe and a down tube are formed of one piece of continuous pipe material with its intermediate portion warped
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH