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