The probe tip of a CMM is in direct contact with the workpiece. They are typically mounted on the shaft end by synthetic monocrystalline, highly spherical industrial rubies. Ruby is a very hard ceramic material to ensure minimal wear on the touch ball. There are many different types and sizes of rubies to meet different applications; The shaft mounted on the probe is typically made of nonmagnetic stainless steel, ceramic, carbon fiber, or tungsten carbide.

Ruby ball probes are suitable for most detection applications. In order to maximize the measurement accuracy of a CMM, users should follow the following principles:

1. Keep it simple

2. Use a short and stiff probe

3. Use the larger ball provided as the tip as much as possible

4. Check that the probe tip is not loose

5. Keep clean

6. Use the appropriate type of probe