nylon or kevlar this allows the strap to be light occupy little space and be economical without compromising the strength of the strap the use of such fabric straps may thus be more beneficial than the known straps of braided steel fig8 illustrates a second embodiment of the present invention fig8 is similar to fig2 and the same reference numerals are used to indicate the corresponding parts again the internal structure may be similar to fig1 and conventional variations may also be used in fig8 the strap has guides 90 integrally fitted thereto which fit on the sides of the mounting device which the strap 50 passes the guides 90 have the effect of distributing the loading due to the strap 50 on the mounting device around the periphery of the cup 4 and thus reduce risk of deformation of the clamping ring 41 apart from the guides 90 the mounting device of fig8 may be similar to that of the first embodiment of fig2 and have a heat shroud similar to that shown in fig5 in the first and second embodiments described above the clip secured to the strap engages the boss a third embodiment will now be described in which the clip engages the cup components of this third embodiment which correspond to components of the first or second embodiments are indicated by the same reference numerals again the internal structure may be similar to fig1 and conventional variations may also be used fig9 shows a general schematic view of the third embodiment and is similar to fig5 however in this embodiment the strap 50 has a clip 100 fixed.