An assembly and method of manufacturing an assembly for use as an isolation barrier to be run in and secured within a well. The assembly has a sleeve member positioned on the exterior of a tubular body, fixed at each end to create a chamber therebetween. Fluid can enter the chamber through a port in the tubular body to morph the sleeve member against a larger diameter surface in the well. The sleeve member is formed of at least two materials, welded together and machined before being arranged on the tubular body. One material is more expandable than the other so as to morph more easily. The sleeve is connected to the tubular body by screw threads and seals. Initial construction of the sleeve member allows welding, inspection and machining without affecting the tensile strength of the tubular body or complete assembly.