The bearing, seal, and lubrication systems of a roller cone bit are important aspects of bit life and efficiency. Roller cone bearing systems are designed to be in satisfactory operating condition when the cutting structure of the bit is worn out. To achieve this standard of bearing performance, modern goals for seal and bearing system life are 1 million or more revolutions of a bit without failure, as opposed to 300,000 or fewer in the recent past. To achieve this goal, research into bearing, seal, and lubricant designs and into materials that improve seal and bearing life is ongoing. Roller-cone bits primarily use two types of bearings: roller bearings and journal bearings, sometimes called friction bearings.