LIAN LI has officially announced the B4-mATX, a new small form factor chassis developed in collaboration with DAN Cases. The new enclosure is designed for users who want to build a compact PC without sacrificing compatibility with modern hardware. Measuring just 21.3 liters in volume, the B4-mATX supports microATX motherboards, graphics cards up to 358 mm in length, and both ATX and SFX power supplies. The company is also offering multiple front-panel designs, allowing builders to choose between high-airflow mesh panels or real wood finishes in black and white color options.
The B4-mATX supports both horizontal and vertical orientations, giving users the flexibility to use it as a desktop chassis or rotate it 90 degrees into a tower. According to LIAN LI, the vertical configuration reduces desk space usage by approximately 30 percent while maintaining full access to all hardware connections. To accommodate both layouts, the chassis includes a rotatable AC power inlet for more convenient cable routing. A swiveling cable bracket beneath the PCIe slots also helps organize display and power cables, keeping the rear of the system tidy.
Cooling flexibility is another area where the B4-mATX focuses on compatibility. The chassis comes pre-installed with two slim 120 mm non-RGB fans configured as exhaust. Builders using an air cooler can reverse the front fan to function as an intake, improving airflow across the CPU area. Depending on the selected power supply, the chassis supports different radiator configurations. Systems equipped with an SFX power supply can install radiators up to 360 mm on the side, while builds using a 140 mm ATX power supply support radiators up to 240 mm. A reversible rear fan bracket can also be repositioned to improve airflow for tower air coolers or create additional clearance for side-mounted AIO liquid coolers.
Despite its compact dimensions, the B4-mATX accommodates high-performance hardware that would normally require a larger chassis. It provides clearance for graphics cards measuring up to 358 mm across four expansion slots. CPU air coolers up to 162 mm in height are supported, with clearance increasing to 168 mm after removing the side fan bracket. LIAN LI also includes a pre-installed adjustable anti-sag bracket that supports heavier graphics cards without blocking the cooling fans.
Storage support includes one 3.5-inch hard drive or one 2.5-inch SSD mounted at the bottom of the chassis, along with another dedicated 2.5-inch SSD mounting location at the front. This configuration gives builders enough flexibility for gaming systems, workstation builds, or compact desktop PCs.
For users planning a vertical system, LIAN LI is also launching the optional B4-mATX Vertical AeroDeck accessory. The expansion kit improves airflow to the graphics card while adding support for up to three 120 mm fans or two 140 mm fans. It also features tempered glass side panels and a magnetic PVC dust filter. The AeroDeck is available in both black and white and matches the wood finish options of the B4-mATX Wood models with walnut or beech front panels.
Key Features
- 21.3-liter small form factor chassis
- Co-developed with DAN Cases
- Supports microATX motherboards
- Compatible with graphics cards up to 358 mm long
- Supports both ATX and SFX power supplies
- Horizontal desktop or vertical tower orientation
- Vertical mode reduces desk space usage by approximately 30%
- Available with mesh or real wood front panels
- Black and white color options
- Includes two pre-installed 120 mm slim non-RGB fans
- Supports up to a 360 mm side radiator with an SFX PSU
- Supports up to a 240 mm side radiator with a 140 mm ATX PSU
- CPU cooler clearance up to 168 mm
- Pre-installed adjustable GPU anti-sag bracket
- Optional Vertical AeroDeck improves GPU airflow and expands fan support
The LIAN LI B4-mATX is available beginning June 26, 2026. Pricing starts at $69.99 (€69.99) for the Mesh Black model, $74.99 (€74.99) for the Mesh White version, $84.99 (€84.99) for the Wood Black model, and $89.99 (€89.99) for the Wood White edition. The optional B4-mATX Vertical AeroDeck is available separately for $29.99 (€29.99) in both black and white finishes.
