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