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