This product is either discontinued or we cannot get that from suppliers.
Noctua NF-A4x10-5V 40mm 5V 4500RPM, Fan Size 40x40x10 mm, Mounting hole spacing 32x32 mm, Connector 3-Pin, Bearing SSO2, Blade Geometry A-Series with Flow Acceleration Channels, Frame Technology AAO , Rotational Speed (+/- 10%) 4500 RPM, Airflow 8.2 m3/h.
Featuring advanced aerodynamic design measures such as Flow Acceleration Channels and an AAO standard frame, the NF-A4x10 5V is a dedicated 5V version of Noctua’s highly optimised, premium quality quiet 40x10mm fan.