CopperTwin® Mini Split Line sets are designed to connect indoor and outdoor units. Copper tube used for air conditioning and refrigeration applications in the field (sometimes called “refer” or “ACR” tube) is an almost pure copper material meeting the requirements of ASTM B 280 – Standard Specification for Seamless Copper Tube for Air Conditioning and Refrigeration Field Service. It is manufactured from copper alloy C12200 having a chemical composition of a minimum of 99.9% Copper (Cu) and Silver (Ag) combined and a maximum allowable range of Phosphorous (P) of 0.015 % – 0.040 %. All CopperTwin™ Line Sets made of copper that meet the requirements of ASTM B280. Both lines are insulated with PE white pipe insulation. This insulation is a white polyethylene hard shell insulation with wall thickness of 3/8″. The expanded closed-cell structure makes it an efficient insulation, also it prevents tearing during installation. Both lines are pre-flared with brass nuts on each end.