0.40mm pitch, 50 positions, 4mm stack — the mezzanine gap is fixed
The DF40HB(4.0)-50DS-0.4V(51): This is a 50-position, 2-row receptacle from the Hirose DF40 series, pitched at 0.016" (0.40mm) and designed for a 4mm mated stack height.

Hirose DF40 series, receptacle, center strip contacts, 50 positions, 0.016" (0.40mm) pitch, 2 rows, gold finish, 4mm mated stack height, solder retention, surface mount, tape and reel packaging.
| Parameter | Value |
|---|---|
| Series | DF40 |
| Mounting | Surface Mount |
| Connector type | Receptacle, Center Strip Contacts |
| Height above board | 0.154\" (3.90mm) |
| Mated stacking heights | 4mm |
| Pitch | 0.016\" (0.40mm) |
| Package | Tape & Reel (TR) Cut Tape (CT) |
| Features | Solder Retention |
| Contact finish | Gold |
| Rows | 2 |
| Positions | 50 |
| Contact finish thickness | 2.00µin (0.051µm) |
The DF40HB(4.0)-50DS-0.4V(51): This is a 50-position, 2-row receptacle from the Hirose DF40 series, pitched at 0.016" (0.40mm) and designed for a 4mm mated stack height.
The mated stack height is 4mm.
Yes, solder retention is listed as a feature. It helps anchor the connector during reflow and provides mechanical resistance to shear forces from the mating half.
RoHS compliance is standard for Hirose DF40 series connectors. The product is lead-free and RoHS compliant per Hirose's material declarations.