The Hirose DF12(3.0)-20DP-0.5V(86) is a 20-position header from the DF12 series, designed for board-to-board mezzanine stacking.
The 3mm stack height is the dimension that matters
The mated stacking height of 3mm is what sets this member apart within the DF12 family — the series offers multiple stack heights, and the (3.0) in the order code marks this variant. The 0.50mm pitch keeps the footprint compact, but it also means the routing channels between pads are narrow; a 2-row, 20-position layout fits in about 5mm of board edge.
Obsolete — what that means for sourcing
The DF12(3.0)-20DP-0.5V(86) is marked Obsolete. That means the factory has stopped production, and the only available stock sits in the surplus and broker channel.
What crosses when the original is dry
Because the DF12 series uses the same 0.50mm pitch and 2-row layout across multiple stack heights, a sibling like the DF12(5.0)-20DP-0.5V(86) (5mm stack height) shares the same footprint and pinout — but the taller gap means it won't fit a 3mm enclosure. If your mechanical stack-up has any z-height margin, a 3.5mm or 4mm variant from the same DF12 family may work, but there is no drop-in 3mm replacement from Hirose. The only way to match the original 3mm height is to source the exact obsolete code or redesign the board for a current-production mezzanine connector.