{HEAD ~ The horizontal flat portion} 24 has substantial length, or {TAIL ~ distance} between adjacent concave arc portions 32 
has
{ HEAD ~ The horizontal flat portion } 24 has substantial length , or { TAIL ~ distance } between adjacent concave arc portions 32
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH