The NBBO is updated throughout the day to show the highest and lowest offers for a security among all exchanges and market makers. The lowest ask price and the highest bid price displayed in the NBBO do not have to come from the same exchange. The best bid and ask prices from a single exchange or market maker are simply called “best bid and offer.” Traders who want to execute orders larger than those available through the NBBO will want to know the other potential bid and ask prices at which they could execute their orders. They can find these in an exchange or market maker’s “depth of book” data. Day traders usually use level 2 market-maker screens to see all the bids and offers for a particular stock.