As you conveniently mount the spectrum tubes into the spring-loaded holders and energize them, a specially designed shield holds the tube firmly while preventing you from touching the electrodes. A black metal panel behind the tube eliminates distracting ambient light and protects the tube from breakage. Comes with instructions. This power supply operates on 115 VAC, 50/60 Hz with its own three-wire grounded cord. Unit is 37.5cm high and holds 26cm tubes.