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