The Hirose DF12NC(5.0)-20DP-0.5V(51) is a 20-position, 2-row header from the DF12 series, designed for board-to-board mezzanine stacking. It uses a 0.50mm pitch and outer shroud contacts, with a mated stacking height of 5mm — the (5.0) in the order code signals that specific stack height.
The DF12NC series offers 20, 30, and 40 positions at the same 0.50mm pitch and 5mm stack height. The 20-position DF12NC(5.0)-20DP-0.5V(51) is the entry point for lower-density interconnects; the 30- and 40-position variants add signal lines without changing the board-to-board gap. All three use the same gold plating and outer shroud contact design, so the choice is driven by the number of signals that need to cross the mezzanine interface.