{HEAD ~ a hub half} forming the support body and {TAIL ~ the hub halves} collectively defining an interior space, 
{ HEAD ~ a hub half } forming the support body and { TAIL ~ the hub halves } collectively defining an interior space ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH