Anyone use these fans?

[smmetz]

any difference between "ball bearing" and "dual ball bearing" for the life of the fan?

Also, how does "rifle bearing" rank for quality?

I've also seem some fans advertised as "brushless", must be refering to the motor. I know brushless motors are better than brush motors, but for all I know brushless is the standard in fans and so this doesnt really mean anything. Anyone know?