These computer system PSU's (Power Supply Units) range from 720W to 950W and fit internally. Ideal for high end power hungry computer systems. Many come with advanced features such as a high efficiency ratings, SLi/Crossfire support, EPS connector and quiet fans. For a PSU, it is important to select the correct size fitment (such as ATX), check it has the correct leads/connectors and enough power (watts) for your systems hardware. It is recommended to over spec the power of the PSU for your system to ensure the reliable operation of your computer and PSU.