I am now planning to try a new broker and on their demo platform they are kind enough to display market depth - it seems though that orders are filled without checking the bid/ask quantity? Certainly, the contracts have a "daily volume", but how come an order is filled with zero bid and ask quantity? I know stock exchanges are obliged by nasd, sec etc...for every buyer to have a seller and vice versa - but does anyone guarantee order exeuction in futures? Clearing houses?? It's confusing...