What's the difference between a side air duct and a side vent?

[JohnJSal]

From the pictures, a side air duct seems to be a vent with a little "tube" or "cup" sticking out from it (on the inside), and the side vent is just the vent without the cup. But what's the difference? Do they both allow for airflow and ventilation on the sides? Doesn't that cup get in the way on the inside?

 

[diduknowthat]

A side airduct allows the CPU heat sink to directly take air in from ouside. However, this usually works only with stock or very small aftermarket heatsinks. A side vent is just holes on the side of the case that allow air to go flow in.

 

[porterjw]

A side airduct allows the CPU heat sink to directly take air in from ouside.

^ Also, there are typically screw holes there that you add a side case fan to the inside of the duct.