{TAIL ~ The portions} of {HEAD ~ the insert} can be a single, rigid, one piece body or the back portion can be pivotal relative to the seat portion 
{ TAIL ~ The portions } of { HEAD ~ the insert } can be a single , rigid , one piece body or the back portion can be pivotal relative to the seat portion
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH