The Hirose DF81D-30P-0.4SD(51) is a 30-position plug from the DF81 series, built for micro-coaxial or ribbon cable termination at a tight 0.016" (0.40 mm) pitch. That shroud is critical at this pitch: without it, a slightly off-angle mate could bend a contact. The gold finish (2.00 µin) on the mating interface keeps oxidation off low-level signal paths, which matters when the circuit is carrying a few milliamps of data rather than power.
This plug accepts discrete or ribbon cable in the 34-36 AWG and 36-46 AWG ranges — the dual gauge listing covers both standard micro-coax and ultra-fine wire. Termination is solder, so the cable end needs to be stripped and tinned or terminated with a compatible solder cup. The 30-position count lines up with common 30-conductor ribbon cable, making this a direct fit for harness builds that need a compact, single-row breakout.