{TAIL ~ The material} selected for the sheath 18 may be the same as or different from {HEAD ~ the material} chosen for the core tube 12, 
{ TAIL ~ The material } selected for the sheath 18 may be the same as or different from { HEAD ~ the material } chosen for the core tube 12 ,
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH