1/2-14 National Pipe Taper Fuel x 1-14 Unified National Special x 1/2-14 National Pipe Taper FuelThe 1 2 14 National Pipe Taper Fuel x 1 14 Unified National Special x 1 2 14 National Pipe Taper Fuel Bulkhead Coupling is a tapered pipe thread designed for fuel and hydraulic applications. A fine pitch straight thread, typically used for specialized applications. The symmetrical adapter, connecting two NPTF fittings with a UNS interface in the middle. Specification Value TYPE Bulkhead Coupling DESIGN Hexagonal adapter for easy wrench tightening