Why does the MicroScribe i+ use the 5mm probe as the Master Probe?

Why does the MicroScribe i+ use the 5mm probe as the Master Probe?

The MicroScribe i+ uses the 5mm master probe to obtain more accuracy. Ultimately, the 5mm probe is stronger than a 3mm and as a result, endures less flexion and wear and tear. However, other probes will work perfectly with the MicroScribe i+ as well.

Note: The 5mm master probe comes in the Metrology Probe Set.