At least portions of the interior surface of the side wall and {HEAD ~ base} define {TAIL ~ a cavity} within the housing 
define
At least portions of the interior surface of the side wall and { HEAD ~ base } define { TAIL ~ a cavity } within the housing
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH