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