The multi-object mode of FLAMINGOS-2 offers the possibility of obtaining spectra of many tens of objects simultaneously. The FLAMINGOS-2 MOS design is based upon precisely fabricating and locating a plate containing many small slits within the spectrograph's entrance aperture. A total of 9 masks can be loaded into FLAMINGOS-2 at any given time: see the diagram of the MOS wheel. The MOS masks are approximately rectangular with dimensions of 2.0 x 6.1 arcmin (671 x 2048 pixels), with a slight rounding at the edge:

Up to ~80 slits can be located in a single mask. Slitlets run parallel to the 6.1 arcminute-long axis of the MOS plate (the spatial direction). The narrow width of the MOS plate, corresponding to the dispersion direction, allows acquisition of targets ±60 arcseconds with respect to the centerline. The MOS plates cover ~42% of the imaging field of view, or ~33% of the detector area.