Ascaso Wega Retention Valve Pipe Parts

Tube D8 L255 (8 mm thick pipe that is 255 mm long) 3/8″ F x 1/4″ F. The 3/8″ female end has a slip or tail-piece type pipe where the 1/4″ female side has a brazed pipe cap end. It’s not exactly clear where this pipe gets situated. It is only listed with a diagram for the “Airy, Antares, Nova and Polar” model boilers.