Noctua NF-S12B FLX 120 x 25mm Fan (600/900/1200 RPM) Highly optimised impeller with Bevelled Blade Tips Thanks to its further refined blade geometry with extended leading edges and Bevelled Blade Tips, the NF-S12B achieves up to 10% more airflow and static pressure than its much acclaimed predecessor at the same noise level 3 speed settings for full flexibility: Providing 1200, 900 and 600 rpm speed settings via the supplied Low-Noise and Ultra-Low-Noise Adapters, the FLX (Flexibility) version can be fine-tuned for superior airflow or maximum quietness. Smooth Commutation Drive 2: The latest version of Noctua's advanced SCD drive system ensures superb running smoothness by eliminating torque variations and switching noises SSO-Bearing: Noctua's time-tested SSO-Bearing technology has become synonymous with supremely quiet operation and exceptional long-term stability