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 one piece of {HEAD ~ continuous pipe material} with {TAIL ~ its intermediate portion} warped 
with
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 one piece of { HEAD ~ continuous pipe material } with { TAIL ~ 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 OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH