DF40HC(4.0)-80DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch rectangular board-to-board receptacle designed for compact, high-density interconnect applications. As part of the DF40 series, it fits designs that need an 80-position, 0.40 mm pitch mezzanine connection in space-constrained consumer, industrial, embedded, and portable electronics. Engineers typically choose this style of connector for stacked PCB architectures where reliable signal routing, low-profile assembly, and SMT processing are important. The listed product status is Active, which supports its use in current designs, although lifecycle confirmation should still be verified through the manufacturer or latest authorized channel data. RoHS compliance information is not explicitly provided in the supplied specifications, so a definitive compliance claim should not be made from this data alone. For regulated builds, engineers should confirm current RoHS and related material declarations directly from Hirose or the latest official documentation before release to production.