Fine Stack (FS) Receptacle for Tight Mezzanine Routing
The 0.020" (0.50mm) pitch and 1.5mm mated stacking height place it in the ultra-low-profile segment — the kind of connector you spec when the gap between parallel PCBs is measured in millimeters, not inches.
At this pitch, the routing density is high enough that the escape pattern on the bottom board needs careful planning, especially if the signal layers are on the inner planes. The 0.047" (1.20mm) height above board is the receptacle's own footprint on the top board before the mating plug is engaged.