6 Non-refillable bottles in the nature of metal cylinders for compressed gas used in the calibration of equipment; Non-refillable metal containers sold as a unit, containing compressed specialty gases, namely, argon, carbon dioxide, carbon monoxide, helium, hydrogen, methane, nitrogen, sulfur hexafluoride, oxygen and mixtures thereof for use in the calibration of equipment; non-refillable bottles in the nature of metal cylinders for compression gases, sold as a unit, containing compressed specialty gases, namely, argon, carbon dioxide, carbon monoxide, helium, hydrogen, methane, nitrogen, sulfur hexafluoride, oxygen, and mixtures thereof for use in the calibration of equipment