Use a suitable tolerance key

What causes this issue?

The master inspection characteristic is linked to a class
characteristic. You entered a tolerance key with a unit of measurement
that does not correspond to the unit of measurement in the class
characteristic.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

You have the following options:
Enter a suitable tolerance key.
Do not use a tolerance key; cancel the entry of the key.

Error message extract from SAP system. Copyright SAP SE.