Example fractional enclosed mass (top) and circular velocity (bottom) profiles computed or inferred under different assumptions. The top and bottom rows show the profiles for Sérsic indices n = 1, 4, respectively, while the columns show intrinsic axis ratios q₀ = 1, 0.4, 0.2 (from left to right). For the top panels, we show the edge-on 2D projected mass enclosed within ellipses of axis ratio q₀ (orange solid line), the 3D mass profile enclosed within a sphere (red dashed line), the 3D mass profile enclosed within ellipsoids of intrinsic axis ratio q₀ (purple dash-dotted line), and the mass profile inferred from the flattened deprojected Sérsic model circular velocity under the simplifying assumption of spherical symmetry (i.e., q₀ = 1; black dotted line). In the bottom panels, we then compare the flattened deprojected Sérsic model circular velocity (black dotted line) to the inferred velocity profiles computed from the 3D spherical (red solid line) and the 3D ellipsoidal (purple dash-dotted) mass profiles under the simple assumption of spherical symmetry. The same total mass M_tot = 5 × 10¹⁰ M_⊙ is used for all cases. The vertical lines denote R = R_e (grey dashed) and R = 1.3R_e (≈r_{1/2, mass, 3D} for q₀ = 1; grey dash-dotted). These enclosed mass and velocity profiles demonstrate that when q₀ ≠ 1, M_sph(< r = R)≠v_circ(R)²R/G. The non-spherical potentials for q₀ < 1 even result in (v_circ(R)²R/G)/M_tot > 1 between R ∼ 1 − 10R_e (i.e., potentially leading to ≳15% overestimates in the system mass). We also see that as q₀ decreases, M_sph approaches the 2D projected mass profile, as the mass enclosed in a sphere versus an infinite ellipsoidal cylinder are equivalent for infinitely thin mass distributions.