Angled compression fittings for rigid tubing work differently that compression fittings for flexible tube. With rigid tube, an external o-ring is placed on the tube after insertion into the fitting. The cap is then slid down over the o-ring to the fitting and tightened. That compresses the o-ring and forces it to expand, trapping the tubing and sealing it at the same time. Angled rigid compression fittings also change the direction of flow in the water loop by changing the direction of the tube itself. With rigid tube the inside of the tubing never touches anything but coolant, so the inside diameter isn’t needed for sizing. TITAN RIG’s selection of angled rigid compression fittings includes examples from the best brands and in several different colors to match the theme of your custom PC.