A standardized system for connecting a compressed gas cylinder to the requisite regulator or transfer line is known as a CGA fitting. CGA (XXX) is a three-digit number that relates to specific gasses for which that fitting is designed.
It is never a good idea to force connections to cylinders. Pipe dope or PTFE tape are never used on CGA fittings that connect the regulator and the cylinder. Metal-to-metal contact and sealing are the goals of the CGA connection. Brass, Stainless Steel, and Chrome-Plated CGA fittings are available. Adapters should not be used to connect two CGA fittings.
For a list of gas types compatible with this SEQ3204SSL fitting, see the CGA connection chart and connection standards downloads, as well as the image below.
