The LMBD4 Barndoors are designed to open and close to throw the light in the direction of your choice. With four doors, you can angle your light for spot lighting, hair lighting, and back lighting. As the LMBD4 Barndoors are part of the LiteMod system, when used with the UMF Unit Mainframe, they can be used in conjunction with the honeycomb grids, gels and filters. The barndoors do not, however, require the mainframe. They can be purchased separately and used directly on the standard reflector of your AlienBees™ unit. (The four doors fold down flat into a compact 9" x 9" x 1.5" size.)