The 903-NM415J-51P: It belongs to the 903NM series, distinguished by the non-magnetic beryllium copper body and centre contact — a deliberate choice for environments where magnetic materials are excluded, such as MRI suites, particle accelerators, or sensitive instrumentation racks.
Why the Non-Magnetic Build Matters
The standard sibling, 903-415J-51P, uses a brass body and brass centre contact — fine for general-purpose RF work, but brass carries enough magnetic susceptibility to distort fields in a 3T MRI bore or a Hall-effect sensor array. The 903-NM415J-51P swaps in beryllium copper for both the body and the centre contact, dropping the magnetic signature below the threshold that would perturb a sensitive measurement. Everything else — the SMB interface, snap-on fastening, 50 Ohm impedance, 4 GHz ceiling, 0.3 dB insertion loss, and 500 mating cycles — stays identical, so it drops into the same PCB footprint and mates with the same SMB cable plug.