EISCO premium spectrum tubes are of high quality and are designed for power supplies holding 26cm spectrum tubes. Features a large 10 centimeters capillary in the center for greater viewing area. These spectrum tubes are designed for operation intervals of 30 seconds and should be used for 30 seconds on/30 seconds off. These tubes effectively demonstrate the spectral lines of pure substances. Tubes require spectrum tube power supply. For intermittent use only, not to be used as a lamp source. Note: expected life of spectrum tubes will vary depending on the gas they contain. If the tubes are used as recommended and not allowed to overheat, the useful life, or time it takes to detect contamination with the usual measuring equipment is very long. Grades 8-16. For ages 13-21.