Two collars are connected to two distal ends of the two end caps and {HEAD ~ two ends} of {TAIL ~ the casing} 
Two collars are connected to two distal ends of the two end caps and { HEAD ~ two ends } of { TAIL ~ the casing }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL