Performance Analysis

The CPU delta T of 57°C is certainly a mediocre result and not helped by the PSU sitting right in front of the CPU cooler, meaning air needs to come in from different angles into it, impacting efficiency. The rear fan proved to be reasonably quiet, but in turn this meant it was of limited assistance to our CPU cooler.

It was unsurprising to see the GPU delta T hit rock bottom too, although it was less than 10°C adrift of the best result here. The first thing we'd do is add a bottom fan and have that pointing at the GPU cooler, which should help to balance the air pressure and will likely improve GPU cooling and possibly the CPU delta T too.

Conclusion

We like that Cooler Master is making efforts to stand out from the crowd and offer something interesting and different and not just with the MasterBox Q500L but the Q300L too. It's certainly budget-friendly, but it's also worth considering if you need ATX compatibility if your priority is reducing dimensions to this sort of level. With the addition of another fan or two in the base it's likely it will perform reasonably well. However, it feels like you're sacrificing a heck of a lot just to shave a couple of centimetres from the dimensions. 

Indeed, Cooler Master's own MasterBox NR400 is only an inch or so taller and deeper but has an extra fan and is easier to use, although admittedly it's limited to micro-ATX and costs £10 more. We can't argue with the Q500L's supremely compact dimensions, and if you're looking to house an ATX board in a case that's as small as possible, it should definitely be on your shortlist. However, it has too many small niggles such as below-par cooling and a fiddly installation to net a recommendation.