Good day
The "stuffing box" should be included with the 013G2951. That is, the insert with the mandrel that is installed in the system. The valve is then mounted on it. This only makes sense if the new valve does not fit or the stuffing box no longer functions mechanically. When replacing the valve, however, the heating system must be taught by the heating engineer and then refilled accordingly. Depending on the case ^^ I am also not a plumber/heater fitter.