The NF-A6x25 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. * Thanks to its streamlined, compact motor design, the NF-A6x25"s motor hub is smaller than with conventional 6cm fans. This allows for more blade surface area and thus contributes to the NF-A6x25"s superior airflow and pressure performance. * Noctua"s AAO (Advanced Acoustic Optimisation) 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. * With the tips of the fan blades ploughing thru boundary layer created by Inner Surface Microstructures, flow separation from suction side of the blades is significantly suppressed, which reduced blade passing noise, improved airflow, pressure efficiency. * Integrated Anti-Vibration Pads made from extra-soft silicone minimise the transmission of minute vibrations while maintaining full compatibility with all standard mounting systems and fan clips used on heatsinks. * The NF-A6x25 features the further optimised 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 stabilisation, precision and durability. * The latest version of Noctua"s advanced Smooth Commutation Drive system ensures superb running smoothness by eliminating torque variations and switching noises. This makes the NF-A6x25 remarkably quiet even at very close distance.