What I did is I replaced the stock differential by this 3racing 39T differential and replace that F6 parts by metal bearing with size of M10 x 15 x 4mm. The outter diameter of the gear joint comes with that 39T differential fits perfectly with the inner diameter of that M10 x 15 x 4mm bearing. However, that two pieces of bearing doesnt come with the differential and you need to order them separately.