memory metal and thus an outer hard covering may be required conversely the conduits may be considerably softer than the shape memory and may be badly damaged by the rings also it may be that contact between the ring and the conduit should in other instances be between members of the same metal in the above instances the shape memory metal is to be clad with an outer sleeve as indicated by the reference numeral 26 a shape memory annular ring 28 rectangular in cross section is sealed in the member 26 see fig4 a which is annular and u shaped in cross section legs 30 of the member 26 are axially larger than the member 28 is thick so that the ends of the legs may be turned over as at 32 in fig4 b to retain the member 28 within the sleeve 26 thereafter the assembly is deformed see fig4 c and may be employed as illustrated in fig1 of the accompanying drawings rather than turning over the edges as at 32 the members may be welded referring now to fig5 of the accompanying drawings the inner and outer surfaces of the hollow annulus 12 of fig1 may be grooved as at 34 so as to insure proper alignment of the rings 16 in the assembly in this instance the rings are slightly larger than the ungrooved regions of the walls defining the grooves and reliance is had on the natural resilience of the deformed rings to permit them to be pushed into place within the annulus or the rings can be deformed and partially recovered to retain themselves in.