Cooler Master MasterBox Q500L Compact ATX Case Review

A small case that supports a full ATX build

Cooler Master has offered many different takes on PC enclosures since they started producing them in the 1990s, and the new MasterBox Q500L is among the more interesting of their recent designs. What makes this compact case special? It is the rare breed of enclosure that holds a full ATX motherboard within a micro-ATX form-factor.

Features of the MasterBox Q500L from Cooler Master:

  • Highly Compact Standard ATX Orientation
  • Movable I/O Panel
  • Versatile PSU Bracket
  • Fully Perforated Chassis
  • Magnetic Dust Filters
  • Edge-to-Edge Transparent Side Panel
  • Clean Routing Space

The Q500L also affords the assembled system a flexible orientation, with support for both vertical and horizontal placement as the rubberized thumbscrews on the rear panel cleverly double as feet. Additionally, the case I/O is housed in a modular panel, and this can be placed in different positions to further enhance the flexibility of this design.


  • Exterior Color: Black
  • Materials – Body: Steel, Plastic; Windowed Side Panel: Acrylic
  • Motherboard Support: Mini-ITX, Micro-ATX, ATX
  • Expansion Slots: 7
  • Drive Bays: 2x Combo 3.5" / 2.5" Bays (each bay supports: 1 HDD or 2 SSDs)
  • Pre-installed Fan(s): Rear: 120mm x1
  • Fan Support
    • Top: 120mm x2 or 140mm x2
    • Rear: 120mm x1
    • Bottom: 120mm x2
  • Radiator Support:
    • Top: 120 / 240mm (35mm max motherboard component height)
    • Rear 120mm
  • Clearance
    • CPU Cooler: 160mm / 6.29 inch
    • Power Supply: 180mm / 7.08 inch
    • Graphics Card    : 360mm / 14.17 inch (270mm clearance with PSUs longer than 160mm)
    • Cable Routing – Behind MB Tray: 27~30mm
  • Power Supply Support: Top front mount, ATX
  • I/O Panel – USB 3.0 x2, 1x 3.5mm Audio Jack, 1x 3.5mm Mic Jack
  • Dimensions (LxWxH): 386 x 230 x 381 mm / 15.2 x 9.1 x 15 inches

Pricing and Availability: $59.99,

Case Exterior

Standing just 15 inches tall this does not look like your typical ATX case. The Q500L is only about 9 inches wide, and just over 15 inches front to back; small enough to make one wonder if it can really support a full ATX build.

The component side panel looks at first glance like tempered glass but is acrylic, simultaneously reducing cost and weight. There is a rainbow effect that shows up easily in photos of this panel, but viewed directly that diminishes to some extent.

The front and top of the case are of identical perforated metal construction, with a pair of screen filters included that attach magnetically for easy removal. These also add something to the look of the case as they are patterned, and custom design are actually available as well (more on this later).

The rear side panel is steel and is attached with four thumbscrews that double as feet should you choose a horizontal orientation.

The rear offers the usual 7 expansion slots of a mid-tower, as well as a 120 mm fan mount. Where is the PSU mount? Hidden from view inside the front panel, with only the power connector located on the back of the case via an extension cable.

The bottom of the case is fully vented and there is a screen filter in place, held on with push-in rubber pegs. It's not as convenient as a slide-out filter, but I can't complain at this price level.

Case Interior

There isn’t much to the component side of the interior, with most of the available space devoted to your ATX board (unless you choose to go mATX or mITX for whatever reason).

There is extra space to the right of an installed motherboard, and this space is put to use for the enclosure’s ATX power supply mount.

One fan is included and pre-installed in the case, a 120 mm model in the back to provide exhaust.

Around back there are storage mounts in the form of two multi-drive trays, each offering support for two SSDs or a single 3.5-inch hard drive.

Build Process

Yes, an ATX motherboard fits inside this small case with little room to spare, and much of the visible space to the right in this photo will soon be occupied by a power supply. Due to the conventional width of the Q500L taller air coolers such as Cooler Master's Hyper 212 RGB Black Edition (reviewed here) fit with room to spare.

Installing the power supply involves first removing the PSU bracket inside the front panel. The vent holes on the panel double as mount points for the bracket, allowing some flexibility with its installation since there is no dedicated mounting point.

Full-length GPUs fit without any issue with a fairly compact 160 mm modular PSU installed up front, which was fully out of the path – though cables need to be managed in the front of the case. We will find out how much airflow might be affected by the presence of an ATX power supply shortly, and it's worth considering an SFX or SFX-L unit with an adapter bracket to free up space and promote airflow – but the point of this design is that it supports standard ATX components all around.

Storage is handled by a pair of dual-drive brackets behind the motherboard, with each supporting either a single 3.5-inch hard drive or two 2.5-inch drives.

The build process with the Q500L is so simple that I won't belabor the point here. After quickly managing the PSU cables and making sure all of my connections were secure, the build was finished.

This is a pretty tidy-looking build:

There is adequate space behind the motherboard tray to manage cables, though with this simple build that uses just a single 2.5-inch SSD there weren't many cables back here with the remainder in the component chamber beneath the PSU.

And we can't forget the design flexibility here, beginning with the case I/O panel. This is a separate component and is removed with four screws.

This can be placed on any of the four sides of the main side, with the acrylic panel simply rotated to match.


Aside from the novelty of a case this small accepting ATX motherboards this is a highly vented design, though lack of front intake fans and position of the installed PSU does officially preclude a ‘high-airflow’ categorization. Still, with the front, top, and bottom offering ventilation with large screen filters – the front and top of the magnetic variety – temps should be pretty good.

PC Perspective Enclosure Test Platform
Processor Intel Core i7-8700K
Graphics Card EVGA GeForce GTX 2070 SC2
Storage CORSAIR Neutron XTi 480GB SSD
Power Supply SilverStone ST1000-P 1000W
CPU Cooler Cooler Master Hyper 212 RGB Black Edition
Operating System Windows 10 64-bit

For reference I compared the results with the MasterBox Q500L against the recently-reviewed be quiet! Dark Base 700 White Edition since both builds used the same primary components (only the PSU was switched in favor of a more compact model).

Higher overall temps than the bigger case, which is unsurprising, but still good. The GPU load temp is misleading as this EVGA GTX 2070 SC2 – like so many GPUs – varies the fan speeds to hit a temp target. This GPU seems to be around 67-70 C regardless of enclosure, so it's time to find a better test of case thermals since most results will be around this 50 C delta (though fan noise will vary from case to case depending on RPMs, of course).

Noise levels were good, and of interest is how much the PSU fan will affect noise levels given the front placement. The rest of the components were about average, with the screen filters on the front and top actually lowering noise slightly (or at least the character of the noise). Airflow is not as good as it could be without the PSU blocking about half of the front panel, and as a result the fans in this build were spinning a bit louder than they would in a higher-airflow environment.

Bottom line, these numbers are good, and I have no concerns about thermals in this case given the ventilation from the top and bottom helping to offset the partial front panel obstruction from the PSU mount.


I love the idea of a small case that holds a full ATX build, and the MasterBox Q500L is an affordable, well-built realization of this concept. It is everything it needs to be from a design perspective, and adds the interesting flexibility of the multiple orientations and modular case IO panel. Yes, the side panel is plastic rather than glass, and the front PSU mount will affect airflow to some degree if you’re using an ATX power supply, but the case still performs just fine and it did not feel like corners were cut with its construction. It is a light yet solid case that can fit just about anywhere, and for this kind of money (currently $59.99 on Amazon) I was very happy with it.