A lockable joint such as a lockable ball-and-socket joint comprising a first arm having a swivel head and a socket, the swivel head being pivotably mounted to the socket, and a locking device arranged for locking the swivel head with respect to the socket, the locking device having a piston, a pressure gas source, and an actuating device arranged for reversibly disconnecting the piston from the pressure gas source where in the pressure gas source is a gas cartridge. A seal suitable at a wide range of temperatures and pressures can be used with at least the pressure gas source.
