intermediate flat portions of {HEAD ~ substantially equal diameter} less than the diameter of {TAIL ~ said corrugations} between said corrugations, 
intermediate flat portions of { HEAD ~ substantially equal diameter } less than the diameter of { TAIL ~ said corrugations } between said corrugations ,
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH