The NF-A4x20 is a fan that utilizes cutting-edge aerodynamic design features such as Flow Acceleration Channels and Noctua's AAO frame system. The PWM version employs Noctua's custom-designed NE-FD1 IC for fully automatic speed control via 4-pin connectors and comes with a low-noise adapter that reduces the maximum speed in PWM operation from 5000 to 4400 RPM. Its exceptional smooth operation, the SSO2 reference-class bearing, and Noctua's proven premium quality make the NF-A4x20 PWM an exquisite choice for the highest demands.