The bearings for rotary mirror scanners must be capable of establishing an extremely accurate rotational axis. This chapter outlines an appreciation of the advantages and limitations of the various types of spin axis bearings available. Gas bearings are particularly suited to low-noise, high-speed, high-accuracy bearing applications, which makes them attractive for many rotary mirror scanners. Gas bearings were a fairly natural derivative of the early work on hydrodynamic fluid film bearings, when it was realized that air could carry loads like any other fluid. A gas bearing is surrounded by its lubricant, the atmosphere. In self-acting gas bearings, stiffness will change with speed and will not necessarily be linear with deflection. Pressurized bearings should have long life in spin axis applications, as, because the bearings are pressurized to separate the surfaces prior to running, no wear should occur. However, it is still desirable to have wear resistant surfaces to withstand accidental turning when unpressurized, or overload touchdown.