The midbody ring is a circular structure located at the core of the midbody in the cytokinetic bridge. It is a highly dense structure that contains microtubules as well as remnants from the contractile ring. The midbody ring acts as a scaffold for factors involved in the final stages of cytokinesis.
The midbody is a transient structure present during the final stages of cytokinesis. The midbody ring can be seen as a circular structure in the bulging region at the center of the midbody that lacks staining of the microtubule marker.
Read more about the proteome of the midbody ring as a substructure of microtubules.