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Silent 4 40 mm Fan

Case Fans

Silent 4 40 mm Fan

4.1 281 ratings

Silent 4: a 40 x 40 x 10 mm fan spinning at 4200 rpm for 7.65 CFM at 18.9 dBA, on a hydro-dynamic bearing.

$9.50

In stock

Sold and shipped by an authorized retail partner. Price shown was current when this page was built.

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Model
FN-SX04-42
Color
Black
Category
Case Fans

Forty millimeters is the size that turns up in the places nobody thinks about until they get loud: network switches, small routers, industrial boxes, 3D printer electronics bays and the tiny corners of compact enclosures. This one moves 7.65 CFM at 4200 rpm and is rated at 18.9 dBA, which is quiet for a fan of this diameter.

  1. Small fans and the noise they make

    A 40 mm impeller has to spin fast to move any air at all, and rotational speed is what people hear. That is why replacing the screaming fan in a switch or a small appliance with a well-made one of the same size is often the single most noticeable change you can make to a room, without touching how well the box is cooled.

  2. Hydro-dynamic bearing over a sleeve

    The bearing is rated for 50,000 hours of service at 40 C, which matters most in exactly this class: small fans usually live in equipment that runs continuously for years. A sleeve bearing in the same slot typically starts rattling long before that, and it always does so at three in the morning.

  3. Check the depth as well as the face

    This fan is 10 mm deep, and 40 mm fans come in several depths. Measure the space, not just the mounting holes, because a thicker replacement will foul a lid or a cable run that the original cleared. The hole pattern is standard at this size; the depth is not.

  4. Direction is a decision, not a default

    A fan can pull cool air in or push warm air out, and in a small sealed box the choice changes where the dust ends up as much as where the heat goes. Note the arrows molded into the frame before fitting, and think about which side of the enclosure has a filter or a clear intake path.

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