DF40B-12DS-0.4V(58) from Hirose Electric Co Ltd is a compact DF40 series board-to-board mezzanine receptacle designed for dense electronic assemblies where space, profile, and connection reliability matter. With a 0.40 mm pitch, 12 positions, dual-row layout, and surface-mount form factor, it is well suited for mobile devices, handheld instruments, compact industrial modules, embedded control boards, and other stacked PCB designs that need low-height interconnection. Gold-plated contacts and a solder-retention feature support stable assembly and dependable mating performance in space-constrained products. Based on the provided specifications, this connector is positioned as an active interconnect option for engineers building small-form-factor systems that require precise board stacking at 1.5 mm. Lifecycle data beyond the listed active part status is not available, so buyers should confirm long-term availability with the manufacturer or authorized sources. Formal RoHS status is also not explicitly provided in the input, so compliance should be verified through the official datasheet or manufacturer documentation before release to regulated markets.