(a) Effective radius vs. absolute V total magnitude of the Virgo UFD1 (large starlet symbol) in comparison with those for other stellar systems. (b) The V-band central surface brightness vs. absolute V total magnitude of Virgo UFD1. Circles and lenticular symbols for the giant ellipticals and bulges in spiral galaxies, downward triangles for the UCDs, pentagons for the Milky Way globular clusters, squares and diamonds for the local group satellites and UFDs, and upward triangles for the dwarfs in M81 and M106 and the low surface brightness galaxies in M101, and small starlet for Virgo dSph-D07.