A straight adapter with a 37-degree AN male flare on one side and a BSP parallel male thread on the other. It exists because BSP is still the dominant port thread on British-pattern, Japanese and much locally supplied equipment, and BSP is not interchangeable with NPT despite the superficial similarity in sizes. A parallel BSP thread seals at its shoulder against a bonded washer or O-ring rather than by wedging the thread flanks, so thread tape is the wrong approach on that end. The AN flare seals dry on metal contact. Confirm the port size on your component before ordering, since this listing carries no published size or thread figure.