The contoured ring 22 bears sealingly with {HEAD ~ the sealing ring} 32 against {TAIL ~ the duct wall} 30 
The contoured ring 22 bears sealingly with { HEAD ~ the sealing ring } 32 against { TAIL ~ the duct wall } 30
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH