Market makers like CINN, TRAC, BRUT... how do these guys get fills? On many of the brokerage platforms you see order routing options like ARCA, INET, NYSE... etc. I rarely see one that routes to a specific market maker. When you send an order to an exchange like Island, is island sometimes routing out these orders to fill the market makers? What are their charges for ecn fees? I don't really understand the role of a market maker. If it is to provide liquity, why not just post on an exchange?