A rubber thread includes in {TAIL ~ cross section} a first rubber portion and {HEAD ~ a second rubber portion} 
A rubber thread includes in { TAIL ~ cross section } a first rubber portion and { HEAD ~ a second rubber portion }
OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD