Stackable 0.100″ Female Header for TI-RSLK v1.1: 2x19-Pin, Straight

via Pololu
$5.71
SKU PL-3676

This stackable 38-pin female header features two rows of 19 pins spaced with a standard 0.1″ (2.54 mm) pitch; this spacing is the same as on most solderless breadboards and matches 0.1″ male header strips. The extended pins allow multiple units to be stacked as popularized on Arduino shields, enabling removable daughter boards that can access pins without blocking them.
The total width is 48.8 mm.