An AN3 double-male flare union, the smallest in the range, for joining two AN3 female ends or ports. AN3 is the size used for brake and clutch hydraulics, gauge and sender feeds and other low-volume signal lines, so a union here is usually about creating a serviceable break point — between a hard line and a flexible hose, at a bulkhead, or where a gauge line has to be disconnected to remove a panel. Both ends carry the 37° AN flare seat, which seals on the cone itself rather than on the thread, so sealant has no place on the joint. On hydraulic systems, always bleed thoroughly after opening any joint and check for weeping under pressure before the vehicle is driven. Tighten to snug plus a light nip.