FAQ: How big is the NH-D15 and how much clearance does it provide for RAM and chipset coolers?
The front fins of the NH-D15 generally protrude over the RAM slots. Due to the recessed lower fins, it is still possible to use RAM modules with up to 64mm height in single fan mode. In dual fan mode, the front fan will sit above the RAM slots as well. In this case, Noctua recommends using standard height RAM (up to 32mm). However, in chassis with more than 165mm CPU cooler clearance, the front fan can be moved upwards to make room for memory modules taller than 32mm (e.g. moving the fan 5mm up will increase the total height from 165 to 170mm and make room for 37mm tall modules).