Our 5/64" (2mm) Silicon Nitride (Si3N4) ceramic balls are 30% lighter than steel and 40% stronger. Each ball is over 1000X more round than the best steel bearing of any type, grade or benchmark. In other words your diff will be smoother and last longer due to the balls not deforming and causing havok to your rings.
These 5/64" (2mm) ceramic diff balls are commonly used 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.