
This is a 2x20 header with female socket (2.54mm pitch) on one end, a spacer and extra tall through-hole pins on the other end.
The female connector is 8.3mm tall, the spacer is 2.54mm tall and the long pin part is 12.2mm tall. Overall, this header is 23.04mm tall.
It can be used specifically if you are making a custom add-on board or a HAT (Hardware Attached on Top) for Raspberry Pi board with 40 GPIO pins. The pins are extra tall to provide further access to GPIO pins for debugging. It is also possible to use it to stack other boards on top of it.