Purchased double to come remove the internal heat of a CHDW. I have chosen for their speed and their mini noise level (0.3 sones 22.5 dBA max). If the air intake is provided by two 12 centimeters this famous brand, the output was optional. But in this kind of case it is essential to ensure good air circulation in video mode ... Especially my i7-4790K is operated at over 90% (88 Watts) over the graphics card MSI R9- 290 (250 Watts) the temperature rises fast enough. My solution is good because so far the maximum reached internally did not exceed 50 ° for an ambient temperature of 21 ° ...