A tool for torquing a regulator onto a cylinder of a portable cylinder assembly. The tool includes a nut and a socket. The nut is configured to fit around a body of a regulator of a portable cylinder assembly. As such, the nut has a first set of grooves that avoids one or more valve assemblies on the body of the regulator. The socket has a cavity extending therethrough such that the cavity consists of three sections: a top section, a middle section and a bottom section. The top section of the socket is configured to be coupled to a device that applies a torque force on the socket. The middle section of the socket is configured to avoid a case of the regulator which is disposed above the body of the regulator. The bottom section of the socket is configured to be coupled to the nut.