Noctua NF-A4x20 5V PWM 40mm x 20mm 4-pin PWM Fan\n\nFeaturing advanced aerodynamic design measures such as Flow Acceleration Channels and an AAO frame; the NF-A4x20 5V PWM is a PWM enabled 5V variant of Noctua's highly optimised; premium quality quiet 40x20mm fan. The custom designed NE-FD3 PWM IC that integrates Smooth Commutation Drive technology and Noctua's reference class SSO2 bearings guarantee superb running smoothness and excellent long-term stability. Topped off with modular cabling; the OmniJoin Adaptor Set and 6 years manufacturer's warranty; the NF-A4x20 5V PWM is a premium choice for demanding 5V applications that require PWM control.\n\n PLEASE NOTE: Being a 5V fan; the NF-A4x20 5V PWM cannot be run at 12V and will be damaged when used with typical 12V power sources such as PC motherboard fan headers.\n40x20mm size Compared to Noctua's award-winning NF-A4x10; the NF-A4x20 is twice as thick; which allows for increased static pressure performance and makes the NF-A4x20 id;