The assembly is provided with {HEAD ~ ribs} extending entirely around {TAIL ~ the bottom surface} of the seat for improved structural support 
extending entirely around
The assembly is provided with { HEAD ~ ribs } extending entirely around { TAIL ~ the bottom surface } of the seat for improved structural support
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH