LIAN LI Industrial Co. Ltd., a leading provider of PC cases, cooling, and power supplies, announces the B4-mATX, a 21.3-liter small form factor chassis co-developed with DAN Cases. Designed to deliver strong hardware compatibility in a compact layout, the B4-mATX supports microATX motherboards, GPUs up to 358 mm, and both ATX and SFX power supplies. The chassis can be positioned horizontally as a desktop unit or rotated 90 degrees into a vertical tower that occupies 30% less desk space. With multiple front-panel finishes, mesh or real wood, in black or white, the B4-mATX suits both performance and lifestyle builds.

One Chassis—Two Orientations
When placed horizontally, the B4-mATX sits as a compact desktop unit. When rotated to a vertical orientation, it occupies 30% less desk space. A rotatable AC inlet adapts to both layouts—rotated outward for easier cable access, or inward in vertical mode to absorb excess cable length inside the chassis. A swiveling cable bracket below the PCIe slots keeps rear I/O and power cables flush against the case in vertical mode, with total clearance including connectors up to 52 mm tall. Front-panel options include perforated mesh for direct intake or a real wood finish (walnut or beech) for lifestyle aesthetics, with both finishes available in black or white.

[Editor's note: Our in-depth review of the Lian Li B4-mATX is now live]

Flexible Design—ATX or SFX, Air or Liquid
The B4-mATX ships with two 120 x 120 x 15 mm slim non-RGB fans pre-installed as exhaust on a removable bracket. The front slim fan can be flipped to act as an intake when paired with a CPU air cooler. Dedicated mounting brackets accept either an SFX PSU or a 140 mm ATX PSU. With an SFX PSU installed, the chassis supports radiators up to 360 mm on the side (52 mm max thickness); with a 140 mm ATX PSU, side radiator support is 240 mm. A reversible rear fan bracket swings inward to improve airflow with tower-style CPU air coolers, or outward to clear space for a side-mounted AIO.

Compact Footprint, Full-Size Hardware
Despite the 21.3-liter volume, the B4-mATX clears 358 mm / 14.1 in GPUs across four expansion slots, and 162 mm / 6.4 in CPU air coolers (168 mm / 6.6 in with the side fan bracket removed). A vertically adjustable GPU anti-sag bracket is pre-installed, with an adjustable supporting arm that contacts the card without interfering with GPU fans. Storage compatibility covers a single 3.5 in HDD or 2.5 in SSD at the bottom, plus an additional 2.5 in SSD at the front.

Optional B4-mATX Vertical AeroDeck
An optional B4-mATX Vertical AeroDeck accessory is available. Designed for vertical-orientation builds, the AeroDeck adds a direct airflow path to the GPU and expands fan capacity by up to three 120 mm fans or two 140 mm fans, built with tempered glass side panels to showcase the installed fans and a magnetic PVC dust filter. The AeroDeck carries the same real wood aesthetic as the B4-mATX Wood variant, in walnut or beech, and is available in black or white.

Availability
The B4-mATX is available on June 26, 2026, at an MSRP of $69.99 / €69.99 for the B4-mATX Mesh Black, $74.99 / €74.99 for the B4-mATX Mesh White, $84.99 / €84.99 for the B4-mATX Wood Black, and $89.99 / €89.99 for the B4-mATX Wood White. The optional B4-mATX Vertical AeroDeck accessory is available on the same date at an MSRP of $29.99 / €29.99 in black or white.