New based on NANOSIZED CRYSTALS IN GLASS MATRIX saturable absorber is transparent glass ceramics containing magnesium-aluminum spinel nanocrystallites doped with tetrahedrally coordinated Co2+ ions. The based on NANOSIZED CRYSTALS IN GLASS MATRIX saturable absorber provides q-switching within the spectral interval of 1200 - 1600 nm in particular for Yb-Er-glass laser. Having the absorption cross-section of Co2+ at the wave length of 1.54 µm significantly higher than emission cross-section of Er:glass, it allows Q-switch operation without focusing radiation into the saturable absorber. Compared with single crystal q-switching materials the glass ceramics saturable absorber is considerably cheaper.