This is a package of fourteen ProTek R/C Tungsten Carbide Differential Balls, the perfect upgrade for ball differentials. These high-quality balls can be used with any ball differential requiring a 3/32" (2.4mm) ball.  PTK-2025
When it comes to diff balls, there are three main materials to choose from: steel, ceramic and tungsten carbide. While steel balls are included with most ball differentials as standard equipment, they provide the shortest life span. Ceramic diff balls on the other hand are the smoothest, but can sometimes leave the diff slipping and feeling like it can't be tightened enough. The third material, Tungsten Carbide, is the happy medium of the three.
Why Tungsten Carbide?
Tungsten Carbide is an extremely hard material, composed of equal parts tungsten and carbon atoms. Compared to steel, it is nearly twice as stiff and much denser. It also features great resistance to heat making it a great solution for cutting tools, machinery, drill bits and especially R/C diff balls. 
Because these ProTek R/C Tungsten Carbide diff balls are so strong and dense, they'll provide excellent resistance against wear and degradation, and long-lasting performance. They might not be as smooth as ceramic, but they will provide a better 'bite' against the diff rings allowing a wider tuning window. They will also withstand the abuse of a lighter diff setting, without excessive diff slipping. 
Features: 
Nearly twice as hard as steel
Polished to a smooth finish
Package contains 14 balls
High heat tolerance
High wear resistance
Wider tuning window
Exact roundness and precision
ProTek R/C also offers 3/32" Ceramic Differential Balls (PTK-2009).

Note: Some ball differentials require 12 balls, others require 14. This package contains 14 diff balls to service both. If your diff requires only 12 balls, you will have two unused balls remaining.