Hands-on with Lian Li B4-mATX Case: Big Power, Tiny Footprint

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Usman Sheikh

As a Senior Hardware Reviewer at Tech4Gamers with over a decade of hands-on experience, I dive deep into benchmarking GPUs, CPU coolers, and motherboards, pushing hardware to its limits. Passionate about overclocking and fine-tuning performance.

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These days, Small Form Factor (SFF) builds often come with a higher price tag, with a strict selection of compatible hardware of your choice. Also, building a PC in a small case has its drawbacks, such as sacrificing thermal performance as well. The Lian Li B4-mATX is looking to change that narrative, the brand has sent us their brand new chassis, Lian Li B4-mATX, it’s a compact case but coming it at a highly efficient 21.3 liters which supports the full Micro-ATX motherboard provided with a enough clearance for the graphics-card up to 358mm, including the 360mm radiator support and up to 140mm ATX PSU support.

Its high compatibility and modular design empower you to customize your build with ease, unlike other small-form-factor cases that limit options and flexibility. Lian-Li has engineered this case to blend high-end gaming performance with refined aesthetics. 

Today we are taking a closer look at this compact powerhouse to see if its thermal performance and building experience live up to its brilliant design, as they claim. 

Let’s go over the key specs of the chassis:

What Makes Lian Li B4-mATX Different?

The Lian Li B4-mATX distinguishes itself in the small form factor (SFF) market through a combination of modularity and a convertible chassis design. Lian Li B4 mATX supports both horizontal and vertical placements to suit different desks and configurations, though you need an extra accessory for vertical mounting. Well not just that this case also provides the exceptional hardware compatibility, such as supporting 4-slot graphics-card, full-sized power-supply, and a 360mm all-in-one liquid-cooler support, giving users confidence in building high-performance systems. Beyond standard boring white and black mesh designs, Lian-Li also offers the real-solid wood paneling to provide a furniture-like aesthetic.

What About Pricing?

Closer Look Outside

Lian-Li has sent us the Wood Black edition, well it’s not their solo venture they have collaborated with DAN Cases, If you aren’t interested in the wood themed one you can pick the mesh version instead, one thing that intrigued me most is it’s impressive hardware compaitibility which you don’t normally get in such small-form-factor chassis as it supports M-ATX motherboards, 360mm All-in-one liquid cooler and up-to 358mm 4-slot graphics-card, which we will demonstrate below. 

Exterior

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This case is designed to support the both orientations for example you can put the case in horizontal and vertical position, out of the box you get the case in the horizontal if the users are looking to setup their case in the vertical, well they might need an extra accessory, vertical AeroDeck accessory, well to install this you first need to remove the standard feet from the original bottom panel of the case. Also, you need to reposition the I/O ports by manually detaching them and relocating them to the dedicated cutout on the AeroDeck accessory. The I/O module features two USB 3.0 Type A Ports, a single USB-C Port, a 3.5mm Audio Jack, and a power button.

To put this in the perspective, this case leans heavily into the modern workstation aesthetic, moving away from aggressive gamer-centric styling in favor of a mature, furniture-like presentation, thanks to its wood design. This case would look good in your living room, thanks to its high-quality vertical walnut slats. Another salient feature of this case is its airflow-first construction; despite its small size, it did not compromise on cooling and functionality. The left-side panel is constructed entirely from edge-to-edge fine black perforated mesh.

Closer Look Inside

The case has plenty of space, considering it’s a small-form-factor case; the main chamber can easily accommodate a Micro-ATX motherboard, as demonstrated in the pictures, along with a massive 2.5-slot graphics card. The card in question is the Gigabyte GeForce RTX 5070 Ti Windforce OC SFF 16GB, which measures 304mm in length and nearly consumes the entire bottom of the PCIe section. The case can support up to a 4-slot graphics card and up to 358 mm in length, so you don’t have to worry about that. If you’re using the case in the vertical position, the GPU would face the front panel from inside; we did not have any issue since the front fans are installed from the outside. However, the bottom fans are most likely obstructed in the horizontal layout. We also suggest keeping an eye on the 12VHPWR cable, and you must route it carefully to prevent it from bowing and pressing against the mesh.

PC Setup

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So far, building in this case has been smooth, just like with any mid-tower case, but cable management could be a challenge. Excess cable length from the ATX power supplies and 24-pin PCI-e cables must be tightly bundled and zip-tied (if you have zip-ties) to prevent them from clipping the side-mounted fans. The case supports a 360mm radiator; however, there is a catch: the clearance is cut off if you’re using the standard ATX power supply, limiting you to a 240mm radiator at most. We are using the Lian-Li SP1000p in the case, so we have plenty of room to install the 360mm all-in-one liquid cooler.

We’re impressed by the modularity of this case, and this is phenomenal when the brand prioritises the user experience. The brackets are fully removable, making hardware installation much easier. The large frame spanning the left side of the main chamber can be lifted out entirely. The power-supply cage also detaches from the frame. This allows you to secure the power supply and pre-route the modular cables from it before installing the unit. Not to forget, the rear fan bracket also features a reversible design, which can be installed outward to create more clearance for the liquid cooling.

The case also features a rotatable AC power connector that lets you rotate the PSU connector outward or inward, designed for both horizontal and vertical layouts. You can move it outward for convenient cable access and/or rotate it inward to avoid clearance issues in vertical mode. This case also comes with 2 pre-installed 120mm fans, which are slim (15mm).

System Assembly

We have finished our system build in Lian-Li B4. Here are several things we have learned so far: first, dropping the core components from the case is quite straightforward once the modular side-cooling bracket is removed. We did not encounter any obstruction when installing the motherboard in the main chamber of the case. We have built our PC in the vertical orientation. The power supply is front-mounted near the top of the chassis; we have utilised the Lian Li SP1000p, an SFX power supply, which provides extended clearance to manoeuvre thick, braided modular PSU cables in the cabin. However, I would recommend getting an SFX PSU instead of an ATX if you want tons of cables inside the case, such as SATA or GPU cables. Cable management here is tricky, and you should not ignore it, as this case is compact; you don’t want the cables clipping on the fan blades. On the front (intake), we are also using 3x Uni Fan TL FLEX.

Since our system assembly is in vertical orientation, we have utilised the Lian-Li (Optional) Vertical Aerodeck accessory, which mounts at the bottom of the case in the default (Horizontal) configuration, effectively standing the case on its end. Hence, the wood panel becomes the ventilated roof. If you’re building in a case, remove all external panels and internal brackets, stripping the case down to the skeleton. This will make PC building much better, as the transition from horizontal to vertical will require some unscrewing anyway. Overall, the building experience was smooth, and the wood touch makes this build look elegant and clean. 

Hardware

Thermal Results 

Should You Buy It?

Buy It If

✅ You want a compact case with a broad compatibility: With a small footprint of only 21.3L, this case supports 360mm radiators and ATX-standard-sized power supplies; you can even mount a thick 4-slot graphics card in the case.

✅ You’re building a PC for your living/tv room: This B4 case is compact, and this specific variant uses a real-wood aesthetic over aggressive plastic designs, which could act as a centrepiece and also offer functionality if you’re looking for a case for gaming on the large TV in your living room. 

✅Don’t want to spend too much on case: This case provides top-notch modularity in a small-form-factor design with tool-less removable panels, dust filters, 2x Lian-Li high-quality fans, and everything is just $70, which is an excellent price.

Don’t Buy It If

❌ You frequently tinker with a components: You might need to remove brackets to access the components. SFF PC builds are cramped, and it’s not as easy as with a full-tower or mid-tower case when you’re swapping hardware at regular intervals. 

❌ You plan to use the standard ATX PSU alongside a large radiator: Due to limited clearance, it’s extremely difficult to mount the 360mm radiator when an ATX-standard PSU is installed. However, the 240mm radiator will work without any clearance issues.

❌ You want a tempered glass side panel to showcase your internal hardware: Lian-Li B4-mATX features a mesh side panel, which is understandable; with that cramped space, you don’t want to choke off airflow to the hardware. If you’re looking to showcase your hardware, then this case might not be good for you.

Final Thoughts

User Friendliness

There are some good things and some challenges and drawbacks when it comes to the user-friendliness in this case, we’ll kick off with the good things first, the tool-less exterior is very interesting if you’re building a PC in this case for the first time, the top-panel is secured with the push-pins, also allows front and side both panels slide off their notches easily also there is another small detail we noticed that Lian-Li has also provided the anti-vibration mounts.

Also, several quality-of-life additions in the case: Lian-Li has provided the Anti-Sag bracket for the graphics card, which is adjustable, to make the building process easier and smoother with a tight 21.3L footprint. This case features removable frames such as the side-fan cooling bracket and top exhaust fan bracket; the front fan bracket can be removed as well. 

Now let’s discuss the challenges we’ve faced. As you might expect, it’s a small case, and you’ll need to put extra effort into cable management. I would like Lian-Li to provide dedicated cable storage behind the motherboard tray. All excess cables need to be managed and bundled in the main chamber of the case; make sure you have cable ties. 

Aesthetics 

Lian Li B4-mATX steps away from the aggressive gamer-centric design, opting for more of an industrial or workstation look. Don’t get me wrong here; I’m not criticising its design, as it’s normal for the m-ATX to look boring, but Lian-Li has provided the wood option, which looks phenomenal. The case is well constructed; instead of the flat and boring panel design, the case uses thick protruding wooden slats coupled with a recessed black mesh, which also serves well when it comes to its cooling performance.

Out of the box, the case is more leaned towards a stealthy, unlit appearance; they did not provide the tempered glass on the side panel, which is a wise choice. Instead, they chose the mesh panel design, which deliberately hides messy cables and internal hardware from view.

If you have noticed in the pictures above, we are not using the case in its horizontal default orientation; instead, we are using it in the vertical position with the add-on accessory called Aerodeck, which introduces a tinted transparent strip alongside the wood slats which allows you to install ARGB fans that cast a sophisticated, defused glow through the wood caps rather than exposing raw LEDs. It’s again, very thoughtful aesthetic design from Lian-Li.

Performance

As you might have seen in our thermal charts above, there is enough CPU thermal dissipation in the case; our AMD Ryzen 7 9700X averages at 74°C under a sustained Cinebench R23 multi-core workload, while our RTX 5070Ti, which is a 300W TDP GPU, is sitting comfortably at 68°C during the superposition extreme workload. These thermal results demonstrate that the case-perforated mesh-side panel easily feeds the graphics card unrestricted fresh air. The results are quite impressive for the small-factor 21.3L case.

Value

Lian-Li B4 m-ATX is literally disrupting the market here at a starting price of $69.99 for the mesh-variants and the extra $10 to $15 for the wood design totally undercuts the premium SFF competitor, as it provides more than the typical SFF cases which are available in market because it natively supports the large components such as ATX power-supplies and the 4-slot graphics-cards and 360mm AIO and m-ATX motherboard support, builders are not forced into buying severely over-priced ITX motherboards or SFX units to build a compact system.

The case also provides an upgrade path, such as the Vertical Aerodeck accessory, which costs around $29.99 and is optional. Not to forget, for $69 you will also get the two preinstalled Lian-Li Slim-Fans and an integrated GPU bracket. 

The Lian-Li B4-mATX undoubtedly delivers immense value; it punches well above its weight class, offering high-end functionality and modularity and decent thermal performance at the entry-level price. We highly recommend this case!

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Usman Sheikh

Senior Hardware Reviewer at Tech4Gamers with over a decade of experience in the tech industry. My journey began in 2014 as a senior administrator for Pakistan’s largest gaming community forum. I specialize in testing and reviewing components like graphics cards, CPU coolers, and motherboards, while also sharing insights on overclocking and system optimization.