Copper tubing is the material used for the Line Sets that connect your indoor and outdoor units. It is the perfect material for HVAC because it is durable, easy to bend, and an excellent conductor of heat. We provide high-quality, pre-flared copper lines in our Installation Kits. It is essential to use insulated copper to prevent energy loss and "sweating" inside your walls. Our Sophia and Olivia series require specific line sizes for peak performance. Proper handling of the copper is vital to avoid kinking or leaking during installation. You can find more technical info on line sizes in our Technical Data section. It is the "artery" system for your Heat Pump System's refrigerant.