The Hirose DF40HC(4.0)-80DS-0.4V(58) is an 80-position receptacle from the DF40 series, a board-to-board mezzanine connector family built around a 0.40mm pitch and a center strip contact layout. Gold plating on the contacts tells you this is designed for repeated mating cycles, not a one-time permanent board stack. The connector is RoHS compliant.
Mated Stacking Height: 4mm
This receptacle is specced for a 4mm mated stacking height — that is the z-height from the top of the bottom board to the bottom of the top board when mated with the matching DF40 header. The 4mm height is the middle option in the DF40 series; the DF40HC(3.0)-80DS-0.4V(58) gives you a 2.90mm stack if you need a tighter board-to-board gap.
Comparing the 80-Position Variants
The DF40HC(4.0)-80DS-0.4V(58) shares the same 80 positions and 0.40mm pitch as the DF40HC(3.0)-80DS-0.4V(58), but the mated stacking height is 4mm versus 2.90mm. The DF40HC(4.0)-80DS-0.4V(51) is electrically identical — same pitch, same height, same gold contacts — but packaged in a Digi-Reel option alongside Tape & Reel and Cut Tape. The DF40HC(4.0)-90DS-0.4V(51) bumps the position count to 90 at the same 0.40mm pitch for a wider signal bus.