These can be used to connect a filament sensor or bltouch to a Creality Ender 3 / CR-10. Please note you will also need to burn a boot loader on some machines.
Here are the notes from the manufacturer:
Works with CR-10, CR-10 mini, CR-10 S4 and CR-10 S5 as well as CR-10S variants, and Ender 3 series.
Pin 27 board makes the installation of a Filament Sensor or a BLTouch fast and easy. Normally to install either of those items you would need to cut a wire from the Ribbon Cable and also get GND and 5v from somewhere else in the CR-10 stock S-Melzi Board.
With the Pin 27 Board all you need to do is 5 easy steps (this assumes you have the control box open and a Bootloader already flashed):
Disconnect the Ribbon Cable from the EXT1 header Board
Connect the Ribbon Cable to the Pin 27 Header Board
Connect the Filament Sensor or BLTouch 3 pin wire to the JST XH connector on the Pin 27 Board (Make sure your wires connect to the right pins. Pinout from top to bottom: 5v, GND, Signal, the Board also has the labels to the JST XH connector) Be careful here as if you use a straight through connector it swapped the connections so i had to swap 5v and ground as shown in one of the images.
Connect the Pin 27 Board to the EXT1 header in the S-Melzi Board
Flash the Firmware with BLTouch or Filament Sensor enabled, that is it.
You must have a Bootloader flashed to your CR-10 Board in order to use this. Support for that is not provided.