I was told (prior to signing up with them recently) that you need the 7 and 55. Although I don't think you really need the 55 to trade only listed. But, (and my memory on this is kind of bad) I think I rememeebr hearing something about everyone eventually needing the 55 for trading. Not sure. It does me no extra good but I have the 7, 55 and 63. From my broker days. No reason for the 24 at all at Worldco.