The weakened zone 22, which is located in {HEAD ~ the centre} of {TAIL ~ tube section} 20, is constituted by a thinner zone obtained by making an annular groove over the outer surface of the section 
of
The weakened zone 22 , which is located in { HEAD ~ the centre } of { TAIL ~ tube section } 20 , is constituted by a thinner zone obtained by making an annular groove over the outer surface of the section
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH