A spirally wound corrugated pipe of {TAIL ~ sheet steel} or the like is provided with outwardly convex corrugations which are spaced apart, with a flat portion of single wall thickness between {HEAD ~ adjacent corrugations} 
A spirally wound corrugated pipe of { TAIL ~ sheet steel } or the like is provided with outwardly convex corrugations which are spaced apart , with a flat portion of single wall thickness between { HEAD ~ adjacent corrugations }
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 HEAD HEAD HEAD HEAD HEAD HEAD