I happen to be an expert on these devices. It half of a JEFF Capacitor. You see the "JE" extension sprocket in the image you provided. This corresponds with the "FF" manifold clog. When they are joined together and work in tandem they provide flexibility and exceptional likability to people named Jeff.

I would like the ATAT with the cone of shame t-shirt in your funny shirt section. Size L please.

Just finished watching the movie, "The Human Experience." This was a nice complement to it. Nice end to my day.