A stainless AN3 to AN3 adapter in SUS303, joining two AN3 line ends without any change in size. In a brake or clutch system this is the piece that gives you a deliberate break point — between a hard line and a flexible braided section, at a bulkhead pass-through, or where a calliper or master cylinder needs to come off without dismantling the entire circuit. Keeping both sides at AN3 means no restriction and no additional adapters stacked in the line. SUS303 stainless was chosen for corrosion resistance, which is worth having anywhere brake fluid, water and road salt meet. Both ends seal on the 37° flare cone, so no thread sealant should be used. Bleed the system properly after fitting and check for weeping under held pedal pressure.