It also forces {TAIL ~ the radially extending rings} through the sealing material and into contact with {HEAD ~ the surrounding tubular} 
It also forces { TAIL ~ the radially extending rings } through the sealing material and into contact with { HEAD ~ the surrounding tubular }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD