The hollow structure includes {HEAD ~ a body portion} that is disposed concentrically about {TAIL ~ the rotational axis} and which is substantially encased in the body structure 
The hollow structure includes { HEAD ~ a body portion } that is disposed concentrically about { TAIL ~ the rotational axis } and which is substantially encased in the body structure
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH