That listing is AFU. It should say DISK only, as it shows the left (what you have) AND the middle device TOGETHER (for disk) OR the far right BY ITSELF for DISK
For all four drum brakes only the far left device by itself is what you want, or if you are converting to disk, continue to use the far left device (what you have) and add an aftermarket proportioning valve inline to the rears.
The far left device is a distribution block and piston operated warning switch.