This coupling has been designed to be a direct fit to the standard Roundhouse buffer beam that has the cutout on the bottom, like the Lady Anna. It comes with a chopper and drawbar coupling and also has a length of brass wire so it can be bent into the 'standard' three link chain hook.
This buffer lifts the buffer centre to the 16mm industry standard of 25mm. 
It covers the hole in the bottom of the buffer.
It comes with a chopper, drawbar and wire for three link.
It adds more cosmetic detail to your model.