NZXT H9 Flow (2025) Case Review: a spacious mid-tower chassis with support for 420mm AIOs

NZXT’s new H9 Flow is one of the largest mainstream cases you can buy, designed to accommodate the biggest and most powerful GPUs – while keeping them cool with targeted airflow while also showing off your build behind two panels of glass.

Most wrap-around (or “fishbowl”) style cases have intake fans that blow directly into the glass on the other side of the case, which, in theory, results in less efficient airflow. With the H9 Flow, NZXT angled these fans, which should provide a more direct path for air as it travels within the case.

It also boasts support for up to two large 420mm radiators for those who want the absolute best cooling possible for their components! Will the H9 Flow make our list of best PC cases? Let’s take a look at the specifications and features of the case, then we’ll go over the features and wrap up our review with thermal testing.

Product Specifications

Features of NZXT’s H9 Flow

▶ Build quality, packaging

The build quality of this case seems decent, but due to its design, if you take apart some of the individual pieces, they can flex if you apply pressure. The glass front and side panels offer a nice view of your PC’s inner components.

The box the unit ships in is mostly simple, showcasing the product’s design in black ink. The case is well protected in shipping with heavy foam, plastic coverings, and cardboard inserts.

▶ Side view

There are few things to point out from the side view: First are the three 140 mm fans, which are larger than the 120 mm fans more typically included for intake in PC cases. At the bottom, there is room for additional fans or a radiator for liquid cooling.

At first glance, it might appear this case only has holes for back-connect style motherboards, but there’s a part on the flap in between the cases and the motherboard support that can pop out for more traditional cable routing.

▶ Up to dual 420mm Radiators supported – radiator and fan support

This case can be loaded with up to two 420mm radiators, supported at the top and side. The bottom of the case supports a 360mm radiator, and there are technically mounts for a single exhaust fan - we’ll touch on that again in a bit.

▶ Dust filters and mesh covers, Bottom View

Bottom Dust Filter

The bottom of the case has two extended legs to lift the case from the ground for proper airflow from the bottom, should you choose to add fans or a radiator. A traditional dust filter is present there, easily removable by sliding. The other intake spots have mesh covers, but not dust filters.

Mesh Top Cover

▶ Rear side view, storage, and cable management features

The first thing that I noticed when looking at the side was the generous amount of storage support for SATA drives. There’s a large plate in the middle of the unit that supports four 2.5-inch drives, and on the side, there’s a bay that supports two more drives of either 2.5- or 3.5-inch varieties. Behind the storage drive plate is a cable routing path with Velcro zip-ties, featuring NZXT’s branding to keep things nice and tidy.

In an interesting design twist, the power supply is mounted in the middle of the unit. As you can see from the photo above, this enables lots of room underneath for cable management – a feature that’s especially useful if you’re using a non-modular power supply.

▶ Front view, IO Panel

As this is a wrap-around case, the front has a glass panel to give you a full view of the inner components. It is different from most competitors of this style by having an angled intake, which allows for more efficient airflow.

The included IO panel lives at the bottom front of the case. From left to right, there’s an audio jack, a USB-C port, 2x USB-A ports, and a power button. The ring around the power button has a white light that activates when powered on.

▶ Rear view

From the rear, you’ll notice that the power supply is mounted vertically in the middle, as mentioned earlier. Most of the rest is fairly standard. Note, though, that while the case only officially supports one 120 mm exhaust fan, you might be able to fit two if you push the default fan to the bottom and use the top holes to screw the top of a second fan.

Included accessories

There’s not much to talk about in terms of included accessories. You get the standard screws and motherboard studs, a few zip ties, velcro strips, and a tool to easily remove or install motherboard studs using a screwdriver.

Thermal tests, test setup, and testing methodology

I’ve focused testing on the efficiency of the case’s thermal transfer, but you should keep in mind that I’m testing the default configuration of these cases with an air cooler and a 300W GPU. I’m considering whether to add additional testing where more case fans are added, or use a more power-hungry GPU, to explore thermal efficiency in more detail for future reviews.

For today’s results, I have tested the system with its pre-installed fans at full speed and also noise-normalized at 38.9 dBA. We’ll cover noise levels, thermal benchmarks of the CPU and GPU, and RPM measurements of the GPU’s fans.

Thermal efficiency testing

Our thermal tests are presented to give you more information about the product’s performance, but aren’t intended as the sole judgment of the chassis. The style, price, features, and noise levels of a case should also be considered, and we all have different preferences.

What I might like in a case, you might not, and that’s OK. My goal with these reviews is to give everyone, no matter their preferences, enough information to decide whether or not a product is right for them. Some folks will want the best thermal performance no matter what. Others might value the looks, design, or features of the case more. Everyone has different ideas of what is the “best” when it comes to your PC’s case!