Silenx IXACCS External 5 Channel Cabinet Cooling S Cabinet must be 2.5" (&gt;64mm) of clearance behind. Requires: 5.0" (127mm) diameter opening or 5.0"x5.0" (127x127mm) square opening Quick and Easy Install: 5-10 minutes to install the entire system Maximum Fans: 5 (additonal sold separately), Included Fans: 2 Model#: IXA-CCS