Sizes and Colors. The largest two Kuiper Belt Objects are Pluto and Eris, each with a diameter of about 1,400 miles (2,380 kilometers). There are six other known KBOs with diameters that are approximately 600-900 miles (1,000-1,500 kilometers), including Charon.luto is in some ways a typical Kuiper Belt Object, but in other ways quite exceptional. The Kuiper Belt consists of myriad worlds with average orbital distances of about 30 to 50 AU from the Sun-that is, beyond the orbit of Neptune.