This Technical Specification describes the use of reinforced thermoplastics pipe (RTP) systems for transmission of gaseous fuels at maximum operating pressures up to and including 4 MPa (40 bar)1), and service temperatures in the region − 50 °C to 120 °C, depending on the liner and cover materials. This Technical Specification relates to transmission systems in which wear and damage to the liner are restricted by limiting pigging operations to soft pigging only. The recommendations in this Technical Specification are confined to RTP and its associated in-line fittings and end-fittings. Where the other system components (elbows, tees, valves, etc.) are of conventional construction, they will be governed by existing standards and codes of practice. This Technical Specification specifies a qualification testing procedure for RTP systems. It also provides a procedure for reconfirmation of the design basis that may be used for product variants where changes have been made in design, materials or the manufacturing process. This Technical Specification provides informative annexes relating to quality assurance, product marking, handling and storage.