Succeeding the vastly successful NF-S12, the NF-S12B is a next generation quiet fan featuring Noctua's advanced SCD2 technology as well as a highly optimised blade geometry with Bevelled Blade Tips that improves its award-winning predecessor's airflow efficiency by up to 10%. Topped off with Noctua's time-tested SSO-Bearing, 6 years warranty and super-slow 700/500 rpm speed settings, the NF-S12B ULN is a premium quality fan for ultra-low-noise applications where maximum quietness has top priority. 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. Providing 700 and 500 rpm speed settings via the supplied adapter, the ULN (Ultra-Low-Noise) version is tailor made for serious silent enthusiasts who demand super-slow running speeds and utmost quietness of operation. The latest version of Noctua?s advanced SCD drive system ensures superb running smoothness by eliminating torque variations and switching noises. Acoustical Noise & RPM - Standard: 6.8 dB(A) @ 700RPM. With Included Ultra Low Noise Adapter: 5 dB(A) @ 500RPM.