Kyosho optional ball differential set for the Ultima SC and DB. Use a traditional ball differential instead of the viscus gear differential in hese cars. Replace the stock gear differential on your Ultima SC or DB. Get the same ball differential performance that the Ultima SP and RT5 have in your SC or DB. Some prefer the ball differential's action over the viscous gear differential. This new ball diff will replace the stock gear diff set up with no modifications, just drop in and see the performance, everything needed is included.Also can be used as a replacement ball differential for the Kyosho Ultima SP and RT5.