Synthetic bids and offers the exchange generates by combining outright and spread markets, so a spread quote can trade against outright quotes and vice versa.
Futures exchanges generate implied prices automatically. If the front month is bid at 5,000 and the calendar spread is offered at minus 3, the engine can imply a bid of 4,997 in the back month even if no one posted one.
For traders this means displayed depth understates real depth, and fills can come from books you were not watching.
Example: you offer the back month at 4,997 and are filled, but no outright buyer existed. The engine matched you against a front-month bid plus a spread order, creating two trades from one. Implied liquidity is a major reason quiet-looking deferred contracts are more tradeable than they appear in depth-of-market.
Original diagrams for the ideas on this page. Illustrative, not real market data.
The bid-ask spread. Buy orders sit below, sell orders above, and the gap between the best bid (50.01) and best ask (50.04) is the spread you pay to cross. Bar length shows the size resting at each price.Rolling a futures position forward. Every futures contract has an expiry date, so a trader who wants to stay in the market closes the front-month contract and opens the next one. That swap is the roll, and the two contracts rarely trade at the same price.
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