Pluto-Charon and Orcus-Vanth are two binary systems in the Kuiper belt. The diagrams represent the current best estimates of their size, with uncertainty. Charon's diameter is known very precisely from stellar occultation measurements. Stellar occultations have not yet been observed for Orcus and Vanth. While they have been observed for Pluto, its atmosphere acts like a lens, bending starlight, and changing the timing of occultation events; until we understand the structure of its atmosphere better (which should happen during the New Horizons flyby) its diameter will remain uncertain by a few tens of kilometers.