A billet separator bored to 15.9 mm for AN8 hose. AN8 is the workhorse size for fuel feed and return on a serious build, and those two lines almost always run together from tank to engine bay, which makes them an obvious pairing for a separator. Locking them side by side keeps the run rigid, stops the two hoses abrading each other under vibration, and gives you a clean anchor point on the chassis or floorpan. It is equally at home on paired oil cooler lines. Fit the separators at regular intervals along a long run rather than relying on one, and check your hose outside diameter against the 15.9 mm bore.