Like DeAnn said, definitely make a list of what you will use it for. Make it as detailed as possible. Include anything you can think of, why you need the arm to do it, and why you need to that task at all. I also recommend referencing independence. Explain how the arm will provide you with that, and, as crazy as this might sound, why that independence is necessary. Also try to get a physician to write a letter that talks about all of this in addition to your own letter. I don’t have JAKO arm, but this is what I’ve done to appeal other pieces of equipment.