5/64" (2mm) Tungsten Carbide balls are an additional option for your diff if ceramics are eating up your trust bearing rings. These balls are not as hard as the ceramics so they could give better life depending on the materials they are combined with.
These 5/64" (2mm) Tungsten Carbide diff balls are commonly used in the Team Associated RC18. This size also works as a replacement for the 6 thrust balls on a Team Associated B4/B44/T4/SC10 or Losi 22/22T/22 SCT diff. Please check your manual for the correct size. These can also be used in a 5/64'th application which equals 1.984mm.