  We study Coulomb branch moduli spaces of a class of three dimensional
$\mathcal{N}=4$ gauge theories whose quiver satisfies the balance condition.
The Coulomb branch is described by dressed monopole operators which can be
counted using the Monopole formula. We mainly focus on A-type quivers in this
paper, using Hilbert Series to study their moduli spaces, and present the
interesting pattern which emerges. All of these balanced A-type quiver gauge
theories can be realized on brane intervals in Type IIB string theory, where
mirror symmetry acts by exchanging the five branes and induces an equivalence
between Coulomb branch and Higgs branch of mirror pairs. For each theory, we
explicitly discuss the gauge invariant generators on the Higgs branch and the
relations they satisfy. Finally, some analysis on $D_4$ balanced quivers also
presents an interesting structure of their moduli spaces.
