An occluder comprising of at least one occluding body, a multiple of elongate members forming an expanding unit capable of expanding into at least one fixation structure for fixing the occluding body within the passage thereby expanding the occluding body), the elongate members penetrating the occluding body, a locking unit for locking the expanding unit in its expanded state, fixation bushes for restricting relative movement between the elongate members and the occluding body, each fixation bush surrounding one single elongate member and abutting the occluding body, at least one thread and wherein at least one of these fixation bushes is fastened to the at least one occluding body with this at least one thread, the thread penetrating the at least one bush and the occluding body.
