The smallest billet separator we list, with a 4.8 mm bore. This size is aimed at fine hard line, vacuum and gauge tubing and the lightest braided hose, all of which have almost no stiffness of their own and will vibrate freely if left unsupported. Two lines clamped into one separator become a single stable unit that can be routed and anchored properly. It is a small detail that makes a visible difference in an engine bay where every other line has been run with care. Take the outside diameter of your line before ordering, as small tubing varies considerably, and clamp gently so the fastener grips without deforming soft-walled hose.