Premium quiet fan, 40x40x20 mm, 12V, 4-pin PWM, max. 5000 RPM, max. 14.9 dB(A), >150,000 h MTTF Award-winning A-series design with Flow Acceleration Channels and Advanced Acoustic Optimisation frame for superior quiet cooling performance 40x20mm size ideal for 1U servers or replacing fans in network and storage equipment (routers, switches, NAS etc.) or other devices such as DVRs 4-pin PWM version for automatic speed control via 4-pin PWM fan headers, 5000rpm maximum speed (4400rpm with supplied Low-Noise Adaptor) Includes anti-vibration mounts, fan screws, extension cable, y-cable and OmniJoin adaptor set for connecting the fan to proprietary fan headers Featuring advanced aerodynamic design measures such as Flow Acceleration Channels and Noctua’s AAO frame, the NF-A4x20 is a highly optimised, premium-quality quiet fan in size 40x20mm. The PWM version sports Noctua’s custom-designed NE-FD1 IC for fully automatic speed control via 4-pin fan headers and comes with a Low-Noise Adaptor as well as an OmniJoin Adaptor Set for easy connection to proprietary fan headers. Its superb running smoothness, reference-class SSO2 bearing and Noctua’s trusted premium quality make it an elite choice for the highest demands.