DF40C-50DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch rectangular board-to-board receptacle designed for compact, low-profile electronic assemblies where space efficiency and reliable interconnect performance matter. With 50 positions, 0.40 mm pitch, dual-row SMT mounting, and a 1.5 mm mated stacking height, it fits designs such as mobile devices, wearables, industrial handheld equipment, embedded control modules, and other densely packed PCB systems. Engineers often choose this series for miniaturized layouts that require stable board stacking and gold-finished contacts for dependable signal integrity. The provided product data lists the part status as Active, which is favorable for ongoing designs, although lifecycle confirmation should still be verified through current manufacturer documentation. RoHS compliance information is not explicitly provided in the supplied specifications, so compliance status should be treated as information not available pending official datasheet, declaration, or manufacturer confirmation before release into regulated markets.