Abstract: A fitting assembly for a high pressure system includes a tube assembly including a tube having an undercut near a first end. A gland is slidably coupled around the tube and has an exterior threaded surface. The gland forms a gland cavity adjacent an exterior surface of the tube. A spring collar is also slidably coupled around the tube between the gland and the first end of the tube such that a portion of the spring collar is disposed within the gland cavity. The fitting body has an inlet passage and a fitting cavity for receiving an end of the tube assembly. The open end of the fitting cavity has a threaded surface forming a threaded engagement with the threaded surface of the gland. This threaded engagement creates a primary and secondary seal in the fitting assembly. The secondary seal applies a force to the threaded engagement.