The fittings are intended primarily for automotive use, and are screwed Dryseal American Standard Taper Pipe thread (NPTF) and Unified threads.
NOTE : Other fittings in common use are screwed with British Standard Pipe taper threads and Unified threads. The BSP thread is similar to the NPTF thread, having the same t.p.i. in the 1 / 2 in and 3 / 4 in sizes, and differing by not more than one t.p.i. in the other sizes. BSP and NPTF threads are, however, not compatible,having different thread forms and methods of sealing, and the fittings are not interchangeable in any sizes.
