The H2 Flow supports radiators radiators up to 280 mm (for 140 mm base) or 240 mm (for 120 mm base).  The combined thickness of the fans + radiator cannot exceed 60 mm.  Radiators must be installed on the front of the case.

What NZXT coolers will fit in the H2 Flow?

If you are looking for an NZXT cooler that will fit the H2 Flow, any of the following models will fit depending on the base size.