The CMCs achieved by force calibration machines depend on the type of force generation - Table 5.1 shows typical values for different machine types. The uncertainty with which values of forces are realised by deadweight force calibration machines may be calculated in a way similar to that of a national force standard machine and may well be smaller than 5 × 10-5. However, if traceability to national force standard machines is required or if the claimed CMC needs to be validated via a comparison with a national force standard machine, the demonstration of a CMC smaller than 5 × 10-5 may be either technically infeasible or simply too expensive. In most cases the requirements of the calibration laboratory are satisfied if a CMC of 1 × 10-4 can be achieved. This enables the calibration laboratory to calibrate force-measuring devices to the best classification specified within ISO 376.