The diameter of the fan in millimeters. The larger the fan, the more effective the cooling and the quieter its operation compared to a smaller one. The most common size is 120mm, with some computer cases supporting larger sizes such as 140mm.

Reverse blade fans reverse the airflow, allowing for intake without the interference of the frame, which reduces aerodynamic turbulence and noise. Additionally, apart from enhancing aesthetics and lighting, they make it easier to clean the blades and offer better cable management, as the wiring remains hidden behind the frame.