These are very handy extension cables for Disk II-drive users. You can swap the drives if needed much easier without opening the case. I found them very usefull when you’re preserving disks (even Applesauce have now taken over this process quite perfectly). These can be made yourself as it’s pretty straight forward if you have the tools.
Connected to regular Disk II interface card.
FinApple 2018 (c)
Apple II Forever