The corrugation 22, {TAIL ~ concave arc portion} 32 and {HEAD ~ horizontal flat portion} 24 are located sequentially along the axis of pipe 20 
The corrugation 22 , { TAIL ~ concave arc portion } 32 and { HEAD ~ horizontal flat portion } 24 are located sequentially along the axis of pipe 20
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH