Bspt X Npt Nipple

Yes, this steel nipple is designed to adapt between BSPT and NPT thread types. It has a 3/8" male BSPT connection on one side and a 3/8" male NPT connection on the other.

That's what this fitting is built for. One end is 3/8" male BSPT (R 3/8 - 19) and the other is 3/8" male NPT (3/8 - 18 NPTF), so it bridges those two thread standards in a straight-through configuration. Both sides are the same size, so there's no reduction happening. Steel construction, 38mm overall length, 17.5mm across the flats. If your application calls for a direct male-to-male adapter between those two thread types at 3/8", this does the job.