Minimum Guaranteed Fill Order- MGF

Market makers help the stock exchange run smoothly. They have assigned stocks and use their pool of shares to help match buy orders and sell orders at moments when there isn't an exact match. Their job is to keep trading chugging along in an orderly and fair manner.

A minimum guaranteed fill order represents a small order from a retail client. Each stock has its own MGF level, determined by the overall liquidity of that particular security. So if an order comes in below the MGF level, that stock's market maker has to fill it, even if they have to dip into their shares to ensure that the order fills at current prices.