According to the description:
This is one of the tribbles used on screen during the filming of this episode. The custom display case measures 10" tall x 11.5" wide x 6.5" deep.
I think this is a very good deal and someone should jump at it! The display case is a great addition and this is well priced at $ 499. As most people know, I think Screen Used are one of the few good guys in the prop industry, so I recommend them.