The system 15, wherein a midsection of {HEAD ~ each} of {TAIL ~ the longitudinal sidewalls} extends towards a central region of the body 
The system 15 , wherein a midsection of { HEAD ~ each } of { TAIL ~ the longitudinal sidewalls } extends towards a central region of the body
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH