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