An inflatable in-ear device includes a core member with a platform provided with a sealing assembly in the form of a locating recess for the registration of a retention ring formed around a defining opening of a sheath arranged in close circumjacent manner around the platform attached to the core member, an abutment surface being formed on a capping for the platform and the core member whereby in use positive location of the retention ring within the recess is achieved by the closure of the recess by the abutment surface. A space is defined between the sheath and the core member for the injection of a settable material used for the inflation of the sheath once the device is emplaced within the ear canal of the ear.