The filet mignon is cut from the tenderloin, which is part of the loin primal. The tenderloin itself runs through the short loin (which also includes the strip) and the sirloin (which includes the top sirloin) sections of the loin primal. This highly-prized cut of beef only represents 2-3% of the total animal.
The size you will receive varies from .82 to .94 pounds