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