The MCRx20-XP (eXtreme Performance) series radiators are high-performance liquid-to-air heat exchangers optimized for use with medium speed 120mm fans and specifically engineered in a slim for factor for high-end liquid cooled Personal Computers. The XP series derive from the Quiet Power technology (QP series) first introduced in 2005 and both series share the exact same dimensions. They differentiate themselves by a higher fin-per-inch (FPI) count where the QP series feature a 12 FPI specification versus 20 FPI for the new XP series. A higher FPI count means that the XP series are more efficient at dissipating heat in the higher RPM fan ranges. When large heat loads are involved for example a CPU and GPU(s) in the loop, this may translate into improved coolant temperature. In general, we recommend selecting a radiator in the XP series for applications where fans will run from 1200 RPM and above, and selecting among the QP series where fans will run from 1200 RPM and below.