Help me identify this drum case size (please)


Well, I have this SKB Roto-X case from years back. I'm not sure what size drum it is for. It measures 20.5 inches across and 18 inches deep.

I have an 18" kick, which measures close to 19" across with hoops. This leads me to believe that the case is not for a 20" bass. I'm just not sure. I need to sell it, but of course I need to know what it fits! Thanks in advance. Cheers,