To show spectral lines of pure substances. These are glass tubes approximately 10-1/4" (260mm) long, central capillary portion approximately 3-1/2" to 4" (90-100mm) long with electrodes sealed at both ends and connected to lead wires protected by metal caps. Needs an induction coil 2" (50mm) spark, or a suitable transformer like a suitable power supply (see below). Length of capillary portion can be varied as required. These can not be used as lamps. For intermittent use. Spectrum - Pink.