This "Set of 6x Spectrum Tubes" is a high quality set.   Includes the following elements: hydrogen, helium, mercury, nitrogen, argon and neon. The discharge is bright and the performance is reliable.   Size is 208mm overall length x 12mm diameter at the large ends.

They are used with the IEC Spectrum Tube EHV unit  (HL3785-001)  which has the correct socket and connection for the tubes.  The tubes mount directly into a deep socket on the top face of the Power Unit to avoid the use of high voltage cables.

Instruction Sheet