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