Impact has the facility to store numerical values in either metric or Imperial units. This can apply to values in Master Tool Settings and also in Standard Variables (Common Variables and Material Variables).
For example, if a Material Variable is set to use dual units and Impact is operating in metric, then the variable can be assigned a default value, a minimum value and a maximum value. If Impact is then switched to operate in Imperial units, the variable can be assigned new values. On switching back to metric the variable still retains the metric values that were assigned to it. These two sets of values are stored independent of each other.