Includes four Spectrum tubes:1 x Hydrogen1 x Neon1 x Nitrogen1 x OxygenTube Length:260mmStrike Voltages:Hydrogen - 2500V - 3500VNeon - 2000V - 3200VNitrogen - 3000V - 4200VOxygen - 3000V - 4200VMaximum Recommended Running Current:3mARecommended Run Cycle:30 seconds on 30 seconds offRequires the following equipment to operate:Spectrum Tube Holder - B8R08098E.H.T. Power Supply - B8R02653E.H.T. Safety Experiment Leads - B8R07149Individual Spectrum Tubes are also available to purchase separately:Argon - B8R06989Helium - B8R06986Hydrogen (included) - B8A46539Krypton - B8R06991Mercury Vapour - B8R06990Neon (included) - B8A46565Nitrogen (included) - B8A46541Oxygen (included) - B8A46553Xenon - B8R06992