Cooler Master Masterbox Q300L Review

Another mini-tower has found its way into our editorial office. With the Cooler Master Masterbox Q300L housing, the manufacturer offers a flexible representative of this class, which is not only airy but can also be operated lying down as well as standing. You can find out how the compact case fared on the following pages. Have fun while reading!

The Cooler Master Masterbox Q300L was used for the test available in the standard version. With this model, the buyer has no option to choose from different models.


Scope of delivery & technical data

The scope of delivery is typical for a case in this price range. In addition to the necessary screws for the hardware and rubber guides for mounting the drive, a couple of cable ties are included. The magnetically adhering design elements for the front of the lid are packed separately in the box.


Cooler Master Masterbox Q300L
Mainboard format (s) Mini-ITX, micro-ATX
designation Q300L
Form factor Mini tower
Price housing about 40 euros
Manufacturer homepage
Other key data
Drives 1 x 3.5 inches
2 x 2.5 inches


1x 120mm back2x 140mm, 2x 120mm front,
2x 140mm, 2x 120mm cover
1 x 120mm
Radiator support Front:
1x 240mm, 120mm
1x 240mm, 120mm
1x 120mm
max.CPU cooler height max.159mm
max.GPU length 360mm
Material housing Sheet steel, plastic
Weight approx. 3.9 kg
Dimensions 230 x 387 x 381 mm (W x L x H)
Others A pre-installed 120mm fan can be used
vertically and horizontally.
Magnetic grille
I / O panels can be used in different positions. Dust
color Black (blue-grayish)

Impressions outside

Unpacked, the Cooler Master Masterbox Q300L reveals a bare steel chassis, which can be covered with two magnetic decorative panels. These are mounted on the heavily perforated front of the cover and are intended to loosen up the look a little or also act as a dust filter. In contrast to most of the cases that we have recently welcomed, the Q300L has a transparent plastic side panel, which makes it significantly lighter but also more prone to scratches.

Light is a good keyword because the Q300L weighs half of the recently introduced Cooler Master Silencio S400, but it also looks less valuable. The sheet steel is kept very thin everywhere, the front, as well as the lid, can be easily pressed in, even if the pure workmanship is okay, the quality leaves me with mixed feelings. But we are in the lowest price structure here, the Silencio S400 is not only twice as heavy but also twice as expensive …

Personally, I like the idea with the magnetically adhering bezels, there is no quicker way to enable access to the assembly of fans and it also looks appealing with this tile design. However, if you often relocate your case, you will enjoy the constantly slipping mats. Because these can easily be pushed back and forth on the front and have to be repositioned with each touch, which can be annoying.

As already mentioned, the side part of the Q300L is made of plastic, which has a slight tint and is held in place with four knurled screws. The Q300L doesn’t provide much in terms of connectivity; the user has to make do with two USB 3.0 ports and one audio input or output each. You won’t find any current interfaces such as USB-C or 3.1 etc.

One of the features of the case can also be seen on the back of the case. The four large rubber feet are used for lying down and thus the Q300L can be used upright or lying down like a desktop case. The side part unfortunately has to be loosened with the four screws in the rubber feet, so a screwdriver has to be on hand for spontaneous handicrafts.

The back reflects the first impression a little. Thin sheet metal and rather simple processing are the programs here, as emphasized by the break-out slot covers.

Impressions inside

When it comes to the interior, Cooler Master relies on functionality and so it is simple but equipped with the most important features. Unfortunately, rubber grommets are not used for the openings.

Due to the compact dimensions of the Q300L, there is of course some flexibility and space left behind. There is no hard drive frame, only a 3.5-inch drive can be found in the Q300L, on the back of the mainboard tray. There are two spaces on the rear for SSDs or other 2.5 inch drives. The case doesn’t offer any more options.

Despite the low entry price of fewer than 40 euros, the Q300L delivers with a pre-installed fan with 1000 rpm, which is mounted in the rear of the case.

Another special feature of the Q300L is the modular I / O panel. Conveniently, this can be mounted in different positions in the housing by loosening four screws, which could prove to be practical for the lying position. This can even be mounted on the back. But then the transparent plastic side part moves with it because it always has to move with it due to the recess.

Hardware installation

When installing the hardware, there are no problems and the assembly of the individual parts is quick, even without instructions. That’s because everything has been kept as simple as possible.

But it is not possible without a tool or screwdriver. Because hard drives, SSDs, expansion cards, everything has to be screwed on because Cooler Master, unfortunately, uses a tool-free approach here.

The back is filled quickly, as all storage media are housed here, hard drives are also screwed directly to the housing, which should also not necessarily have a positive effect on the background noise, depending on the hard drive model.

As already mentioned, nothing works with the Q300L without the right tools, because the power supply unit also has to be screwed onto a panel, which is then screwed to the housing and the expansion cards have a somewhat complicated holder. Cooler Master has certainly used a widely used “tooling tool” to be able to offer the price as low as possible.

Overall, the assembly is easy, there is enough space to build in some bulky hardware without breaking your fingers. Due to the deep rear, clean cable management is also possible, as long as you don’t use all the assembly areas with drives, because then it could get a bit tight.


Installation of a water cooling

A water cooling can also be accommodated in the Q300L, Cooler Master states a 240mm radiator in the front on the homepage. This should fit loosely because our 280mm radiator also fits into the front of the lid.

BUT: Due to the perforated metal sheets in the front and cover, which unfortunately do not provide any holes suitable for a 280mm radiator, something has to be tinkered or adjusted. Then a radiator in the lid is also possible, but that is very tight due to the fan that builds up but works just fine if you are not afraid of some rework.  A 240mm radiator including a fan does not cause any problems, but if you position it in the front, it becomes difficult with custom water cooling for the other elements such as pump, expansion tank, etc. in terms of space. AiOs do not pose any problems.

Our case tests are carried out according to a standardized principle. As usual, how we test can be found in our articles,  How We Test. In this way, it is possible to compare all test reports in the area of ​​housings.

Overall rating

The overall rating is a summary of all temperatures and measured values. In total, this results in a performance indicator about the cooling capacity of each housing. We are currently endeavoring to fill in the basis of comparison so that all values ​​determined are also about one another.

Brief evaluation

Even if the Q300L is significantly more airy than the Silencio S400 housing with the additional insulation, only one fan is not able to achieve top values ​​for the temperatures, which further measurements will show. The built-in fan also only rotates at a maximum of 1000 rpm, the fans built into the Silencio S400 can operate at up to 1400 rpm. This is clearly reflected in the measured values.


Volume measurement maximum speed

Brief evaluation

If the conditions for the fan settings are the same, both cases behave very similarly; the Silencio produces a bit more volume in the measurements with the two built-in fans. But here, too, I have to say clearly that the Q300L is, subjectively perceived, is louder in direct comparison, since every little beeping, clacking, etc. penetrates outside unfiltered, the Silencio S400 filters away significantly more and only offers a pleasant background noise.

Temperature measurement

To show the thermal capabilities of housing, we have documented two load scenarios or rather two ways of looking at them. Basically, the combination of Furmark  (@  1024 x 768px  – non-fullscreen) +  Prime95 “Custom”  (with 8 threads, further setting) is operated simultaneously for the tests, which, in turn, represents a very good mix of system utilization and practical relevance.

  • Measurement 1: Maximum speed
  • Measurement 2: 800 rpm (the value is set in the mainboard BIOS)

This process is now operated for  20 minutes,  recording the MAX value over the 20 minutes and, in a separate process, the  Delta T  value, i.e. the difference between the measured value and the room temperature. After completing the measurement process, the values ​​are read from AIDA 64. The unit of measurement is logically set to degrees Celsius. Of course, the method used is not immune to measurement tolerances, which means that fluctuations in the range of 0.5 degrees Celsius in the measured temperatures are possible.


Temperature measurement 800 rpm

Brief evaluation

The temperatures are very similar with the same fan speed. Thanks to its airy housing concept, the Q300L can compensate for the lack of a fan in the front and offers solid performance. This should be easy to improve with an additional fan.


Temperature measurement, highest speed (1,400 rpm)


urze evaluation

At full speed and in direct comparison to the Silencio S400, it does not even come close to the cooling performance of a two fan operation or the fan limited to 1000 rpm limits the performance. But it’s no surprise that two 1,400 RPM fans are superior to a 1,000 RPM fan.


With the Masterbox Q300L housing, Cooler Master serves the entry-level segment of mini-towers, which for the most part really works. You shouldn’t expect too much in terms of processing quality, but it fits the price structure and is kept quite simple. The optics, with the removable designer mats and the large plastic viewing window, are also okay, even if you take a closer look at the price range in which the housing is located. Features such as the easily repositionable I / O panel and the option of using the housing vertically or horizontally are major plus points for the Q300L. This also makes the area of ​​application flexible.

As expected, cooling performance and background noise are not the best, but with only one fan from the factory and the open case structure, they are not top values. However, all results remained within limits and with just one more fan, significantly better results should be achieved in terms of temperatures. We would not recommend the case for high airflow, although the case has a complete perforation in the front and cover, this is much too coarse so that every fan will have its trouble transporting the necessary air volume – including the background noise is also negatively influenced by it. For high-performance systems (in the micro-ATX area), I would personally prefer to use another model such as the Masterbox MB400L orGrab Koolink Citadel Mesh. It is a shame that the Cooler Master fails to install a 140mm fan despite having enough space. The installation of the hardware, especially the hard drives directly on the mainboard tray and the slot covers that have to be broken out again, also tarnish the otherwise solid overall impression.

At a price of a little under 40 euros, you get a special case with some useful features, but simple equipment and minor flaws. Those who prefer flexibility and optics can take advantage of this course without hesitation.


Cooler Master General Summary

Cooler Master To summarize, we see that it has very good features in terms of design, price and performance. Cooler Master, which has given a successful performance compared to its competitors in this segment, has not received any serious complaints from its users until now and has given its users confidence with maximum positive feedback. With the Cooler Master 2-year warranty, it continues to support any problem after the sale and does not suffer the user.

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Frequently Asked Questions


Installation of the Product is Extremely Simple. You can set it up easily with the included Guide.

Has no known chronic problems.

The minimum warranty period is 2 years.

You can buy it from sites like amazon, ebay.