HO-SP-MSTH-06 Multi Spectrum Tube Housing for Spectral CalibrationMulti Spectrum Tube Housing for Spectral Calibration Holmarcs Multi Spectrum Tube Housing holds six spectrum discharge tubes simultaneously. It can quickly switch from one gas to another without displacing the lamp housing. Power supply is common for all discharge tubes, kept inside the unit. The gas tubes are permanently enclosed to protect the tubes from breakage. Optical fiber can be directly attached to this unit for fiber optic spectrometers.