This is a black nickel-plated angled G1/4 to G1/4 thread extension. The fitting has a 45-degree angle and can be rotated on the threaded side. This greatly facilitates installation and allows for precise alignment.
Note: The rotation function of the fittings should always be used when they are removed, as it can be relatively stiff. No force should be applied to the fittings while they are installed to avoid damaging the fittings themselves and the attached coolers.