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