Just like with the single 120mm Kuhler H2O H600 Pro model and its predecessor the Kuhler H2O 650 the Kuhler H2O 1200Pro is also quite different with its predecessor the Kuhler H2O 1250. The main difference is clearly the two separate 120mm PWM blue LED fans (1800RPM @ 35dBA) which can be easily replaced/exchanged if they are too slow for you or if they stop working something which you couldn’t do with the built-in fans (intergrated fan/pump combo) of its predecessor. Another difference (not as important) is the use of 315mm long FEP (fluorinated ethylene propylene) tubes instead of the 300mm long PA (polyamide) ones found in the 1250 model. Link