A flare nut is a specialized brass fitting used to join copper refrigerant tubing to the indoor and outdoor units of a Ductless Mini Splits system. This type of connection requires the copper to be "flared" out at a 45-degree angle, creating a mechanical seal that can withstand high pressures without the need for Brazing. Most ACIq and MrCool systems come with flare connections to make DIY and professional installations faster and cleaner. It is critical to use a torque wrench when tightening these nuts to prevent refrigerant leaks—the most common issue in mini-split setups. You can find replacement flare nuts and flare-to-braze adapters in our Installation Kits collection. Using a high-quality sealant on the flare face can provide an extra layer of protection against "slow leaks" over time. Because they don't require an open flame, flare nuts are the preferred choice for indoor wall-mount installations. They are the backbone of the "quick-connect" philosophy in modern cooling technology.