The larger, dual tower version promises the "top performance-to-noise ratio and the highest reliability available", according to the company's press release. The cooler is rated capable of handling loads up to 220W and it makes use of two fans in order to do so; however, only the external fan is 135mm, while the internal fan remains an 120mm model. The company claims a maximum noise level of only 26,4dB(A).The smaller Dark Rock 2 is a single tower version, yet it is still rated capable of handling loads up to 180W. This version makes use of a single 135mm fan, with the claimed acoustic levels dropping down to a mere 21.2dB(A).Source : Company Press Release
Read more: Be quiet! introduces new CPU cooler generation Dark Rock 2 by VR-Zone.com