Schematic view of the inner Milky Way, showing two possible configurations: a ring (red dashed line) and two arms (solid black lines). While both are almost indistinguishable in the first quadrant, it is possible to distinguish between them in the far end of the bar and the tangent line to the arm. The light-red shaded areas represent the areas where the maxima of the potential of the bar (L₄ and L₅) sweep away stars and gas. The bulge has been left out of this representation.