A straight adapter that puts a 37-degree AN4 male flare on one end and a BSP parallel male thread on the other, so a -4 AN line can be run to a BSP-threaded port. BSP is the thread you meet most often on British, Japanese and locally sourced components, and it is not interchangeable with NPT even where the two feel close by hand. Because a parallel BSP thread does not wedge itself tight, it seals on a bonded washer or O-ring at the shoulder rather than on tape or sealant down the threads. The AN4 side suits low-volume duties such as gauge and sender feeds, oil pressure take-offs and small return lines.