An implantable device intended to be used to permanently join vascular structures (blood vessels) through the coupling of two ring-shaped components that are inserted into the ends of the vessels to be attached. It is also used in microvascular surgery. This device is made of a substance or material that cannot be chemically degraded or absorbed via natural body processes (e.g., stainless steel). Some types are preloaded on, or supplied with, disposable devices associated with implantation (e.g., coupling approximator).