In an example, a data unit includes a data unit mounting having a circuitry region, a registration portion, and a retaining feature. Circuitry comprising a data source to provide at least one additive manufacturing parameter is arranged on the circuitry region of the mounting. The data unit mounting is to be removably mounted on a receiving portion of an additive manufacturing build material component, such that the registration portion is to be received in a corresponding guide portion of the receiving portion of the additive manufacturing build material component, and the retaining feature is prevent removal of the data unit from the receiving portion unless deformed. Deformation of the retaining feature to effect removal of the data unit from the receiving portion may be a permanent deformation.