Elliptical galaxies generally do not have very much interstellar medium compared to spiral galaxies. The Milky Way, for example, is a spiral galaxy, and contains an amount of interstellar medium several billion times the mass of the Sun. An elliptical galaxy about the same size as the Milky Way, in comparison, would likely not have even half that amount. Irregular galaxies have the largest proportion of their mass as interstellar medium. In most galaxies, the majority of their interstellar gas and dust collects in the disks of the galaxies rather than in bulges or halos.