A multi-scale bass uses a longer scale for the lowest string and progressively shorter scales toward the higher strings. At the same gauge and pitch, a longer scale makes a string feel firmer, which is one reason multi-scale designs exist.
S.I.T. multi-scale sets use a 1.5-inch bridge taper on the low strings, and the nut-end tapers fall at about 38 and 39 inches. Our multi-scale sets, Power Wound and Power Steel, come in 4-string and 5-string. We don't currently make a 6-string multi-scale set.
For either type, what matters is that the winding length and taper locations fit your instrument's geometry. Don't rely on a "multi-scale" label alone. Measure your current string from the ball end to the taper, or contact S.I.T.