DF37NC-50DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch board-to-board rectangular connector designed for compact electronic assemblies where low profile and dense interconnect spacing are critical. As part of the DF37 series, this 50-position, 2-row surface-mount receptacle is well suited for portable devices, industrial control boards, embedded modules, medical electronics, and other space-constrained systems that require reliable mezzanine connection between PCBs. Engineers typically select parts in this category for signal routing in tightly stacked designs, especially where controlled board height and consistent mating performance matter. The supplied product data lists the part as Active, which is a positive indicator for ongoing design support, although lifecycle should still be confirmed directly with Hirose for long-term programs. RoHS compliance information is not explicitly provided in the supplied specifications, so compliance status should be treated as information not available pending manufacturer documentation or the latest official datasheet.