The NF-A9 is a highly optimized, premium quality quiet 92mm fan. Featuring Noctua's AAO (Advanced Acoustic Optimization) frame as well as sophisticated aerodynamic design measures such as Flow Acceleration Channels, the NF-A9 further improves the renowned quiet cooling performance. The PWM version sports Noctua's custom designed NE-FD1 IC for fully automatic speed control via 4-pin fan headers and comes with a low-noise-adaptor to reduce the maximum speed during PWM control from 2000 to 1550rpm. Its superb running smoothness, reference-class SSO2 bearing and Noctua's trusted premium quality make it an elite choice for the highest demands.