Generally "bass clarinet" pads made by Pisoni, Music Medic and other manufacturers are made thinner (usually around 3.2-3.5mm) than sax pads (3.8+mm). Most bass clarinets including Vitos need a mix of the thinner bass clarinet pads on the top and sax pads on the bottom. For example, On a Buffet I just overhauled I used Ferree's B32s (3.2mm) for everything from RH2 up and B42s (4.7mm) For RH3 downward. This is pretty standard on most bass clarinets. I would not try to use sax pads on the top end of the instrument.