In the spectra of many Oe and Be stars we observe complex profiles in the lines of many ions. The observed features are the composition of a number of absorption components. This fact is interpreted by the existence of independent density formations in the region, where a specific ion line is created. These density regions rotate and move radially with different velocities and so they create components with different widths and radial shifts. We name these components Satellite Absorption Components (SACs or DACs). In this paper we present the model proposed by Danezis et al. (2003), which describes the structure of these density regions. With this method we can calculate the apparent rotational (Vrot) and expansion/contraction radial velocities (Vexp) of these density regions, as well as an expression of the optical depth (&xgr;). Also we present three applications to the spectra of hot emission stars. © 2004 American Institute of Physics