Noctua AAO Frame Design, SSO2 Bearing Premium Quality Quite Fan NF-A8 PWM The NF-A8 impeller features suction side Flow Acceleration Channels. By speeding up the airflow at the crucial outer blade regions, this measure reduces suction side flow separation and thus leads to better efficiency and lower vortex noise Noctua's AAO (Advanced Acoustic Optimization) frames feature integrated anti-vibration pads as well as Noctua's proprietary Stepped Inlet Design and Inner Surface Microstructures, both of which further refine the fan's performance/noise efficiency Noctua's Stepped Inlet Design adds turbulence to the influx in order to facilitate the transition from laminar flow to turbulent flow, which reduces tonal intake noise, improves flow attachment and increases suction capacity Integrated Anti-Vibration Pads made from extra-soft silicone minimize the transmission of minute vibrations while maintaining full compatibility with all standard screws and other mounting systems The NF-A8 features the further optimized second generation of Noctua's renowned, time-tested SSO bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilization, precision and durability Supporting fully automatic PWM speed control, the NF-A8 PWM uses Noctua's novel, custom designed NE-FD1 PWM IC that integrates Smooth Commutation Drive (SCD) technology. The NF-A8 PWM is supplied with a Low-Noise Adaptor (L.N.A.) that reduces the maximum fan speed from 2200 to 1750rpm. The L.N.A can be used either to run the fan at a fixed speed of 1750rpm or to cap the maximum speed when using automatic PWM control The fan's short 20cm primary cable minimizes cable clutter in typical applications while the supplied 30cm extension provides extended reach when necessary.