The arms in galaxies of this luminosity class are not as narrow or well defined as those of ScI. Two examples of thick-arm spirals are NGC 0157 and NGC 4254 in the Virgo Cluster. Of the remaining four, NGC 2223, NGC 2903, and NGC 3756 have thin arms, while the arms in NGC 5248 (of Sbc type) are thick over the inner bright disk but become very thin and are of low surface brightness beyond the lens.
The arm pattern for all galaxies of this class is still nearly as well defined as in ScI systems but, as in NGC 4254, has a raggedness not present in ScI systems.
The spread in absolute luminosities for galaxies of types ScI and ScI-II is large, ranging from - 18m.3 to - 23m.4 (Tammann, Yahil, and Sandage, 1979), with the bulk of the distribution from - 20m > MBT0, i > -23m. This is a factor of 15 in luminosity (and presumably a comparable range in mass). The similarity of all galaxies here and in the ScI panel shows that the form does not appreciably change over this large range in absolute magnitude, and hence that luminosity is not the chief factor that governs the luminosity class of a galaxy.
NGC 4254 M99