UM71 is another kind of jointless track circuit. It is a jointless, seamless pipe lining within an existing pipe. These may be monolithic (single-piece) or jointless structures. Gosen was one of the world's first companies to make jointless carbon rackets. The company's first successful pen, released in 1899, was the Parker Jointless. The Orange Line's tracks will meet China's national standards, and will employ jointless track circuits. The TI21 and Westinghouse FS2500 jointless track circuits are similar to the UM71.