Best answer: The NZXT H1 will only take Mini-ITX motherboards. All other ATX motherboards simply will not fit inside the compact chassis.
Go for a Mini-ITX motherboard
Like other Mini-ITX cases, the NZXT H1 is designed to be compact. You won’t be able to cram the largest PC components inside, nor will it be possible to work in a custom water-cooling loop with a sizeable radiator and reservoir. You’re short on space and the only motherboard size available to you is Mini-ITX.
Mini-ITX motherboards are essentially smaller versions of microATX motherboards, which are in turn smaller versions of ATX motherboards. You don’t lose out on any of the base functionality of a motherboard, but vendors won’t be able to fit everything on the smaller circuit board. You may have two SATA ports instead of eight or a single PCIe slot instead of four.
For the H1, the motherboard dimensions need to be 170 x 170 mm. Any Mini-ITX motherboard on the market will do, but you’ll need to select one based on which processor you plan on using. We’ve supplied two fine examples here, one for AMD-powered systems and another for Intel.
Compact PC case with bags of potential
The H1 from NZXT may seem rather expensive, but for the price, you not only get a high-quality Mini-ITX case, but also a preinstalled 650W PSU and AIO cooler.