The StarTech.com 8cm x 8cm x 2.5cm (3 1/8" x 3 1/8" x 1") PC case fan is an add-in cooling fan designed to fit most computers. It can be used to circulate cool air into the case or exhaust warm air out, preventing problems due to overheating components. A quiet running brushless ball bearing DC motor coupled with a high efficiency blade design is capable of moving 37 CFM (cubic feet per minute) of air. Power is supplied to the fan using a power tap that is connected to the large LP4 power connector on a PC's power supply.