This straight adapter carries an AN6 37-degree male flare on one end and a 5/8*20 male thread on the other. The 5/8-20 thread is a common fuel inlet size on square-bore and older four-barrel carburettors, so this is the part that lets you abandon rigid factory-style plumbing and run a proper -6 AN braided feed instead. AN6 is the usual choice for a carburetted feed line: it flows enough for most street and club-level engines without the bulk of larger hose. Check the actual inlet thread on your carburettor before ordering, as 5/8-20, 7/8-20 and 9/16-24 inlets all appear on similar-looking bowls and none of them are cross-compatible.