For over 80 years, Mueller Industries has been a market leader in the manufacturing of tube, fittings, valves and protection devices for the HVAC & Refrigeration industries. Known for quality, precision fit and reliable performance, Mueller's copper tubes and fittings are produced in accordance to the applicable ASTM/ASME specifications, and suitable for higher pressure refrigerants such as CO2. The Streamline® Standard and Mini Split Lines Sets are UL Recognized up to 700 PSI for sub-critical CO2 systems.