The authors reviewed the areas of application of digital twins in discrete manufacturing. Examples of specific implemented projects have shown that the urgent task is to create mathematical models of the process of technological preparation for flexible discrete production, covering a description of the stage of testing the product design for manufacturability. The authors developed a formalized description of flexible discrete manufacturing and a generalized model of flexible discrete manufacturing and identified areas of application of the developed models. Digital twins of products manufactured in flexible manufacturing can include developed models.