Since the comparison master is only in possession of the US Army, a number of commercial masters have been developed that are intended to be compatible, but due to the complexity of the factors that make a scratch visible, these masters are not always compatible with the original and there is no way to match one set to another. For example, a visibility grade 10 scratch on one master can appear brighter than a visibility grade 60 scratch on another master. For this reason, it is recommended to also indicate on the drawing the type of master set to which it must be compared during the test.