Disclaimer: Although the review sample was provided by Cooler Master, the review itself is 100% unbiased. All opinions are my own.
The MM520 comes with the Pixart PWM3360 sensor which is the current top of the line optical sensor from Pixart. The 3360 supports up to 12,000 CPI and features a very high PCS (perfect control speed) of 250 IPS or 50G. The switches for the main buttons are Omrons that are rated for 20 million clicks. The cable has a length of approximately 1.8m. The mouse has one button for switching CPI steps and two side buttons on the left side. All the buttons can be fully remapped in the software (details see below). Lastly, the MM520 features RGB lighting with 16.7 million colours.
The packaging includes the mouse and a short manual as well as a set of spare mouse feet (the latter is only true for more recent batches). It is also worth mentioning that Corepad already offers replacement mouse feet with rounded edges for the MM520. As can be seen in the pictures, the cable is unfortunately not wrapped around the casing but folded somewhat tightly. The kinks in the cable went away pretty quickly though.
Shape and weight
The MM520 is an ergonomic mouse intended for right-handed users. More specifically, the shape is tailored for claw grip. The size is medium. There are two side buttons on the left side and a slight curve where the thumb rests which helps with picking the mouse up but no rubber grip. On the right side there is a finger rest and a little patch of textured rubber grip. Although it seems odd that the rubber grip is on the right instead of the left side, it is indeed quite nice for comfort. The hump is more towards to the back and provides ample palm support.
The feel in hand is actually somewhat comparable to the MasterMouse S which has a fairly wide hump that is placed more towards the back as well. Much like the MasterMouse S the MM520 works well in claw grip (which is my preferred grip), although both palm and fingertip should work well enough too. The biggest difference between those two mice is surely the finger rest on the right side. The finger rest is quite useful for those people who try to keep their fingers off the pad (like me). At the same time it makes the mouse VERY wide, though – much wider than any other mouse I’ve ever held in hand. Due to this I had some trouble adjusting to the shape of the MM520. In fact I spent quite some time finding a fully comfortable grip but had to give up eventually. Surprisingly enough the grip that felt most comfortable was a full palm grip, but I simply can’t aim with a palm grip. Whether you run into similar issues will most likely depend on your grip style (for instance, I reckon that you’d have an easier time with a 1-3-1 grip). Still, I’d only recommend trying this mouse if your hand is wider than average (10+ cm). For reference, my hand size is 19x10 cm.
On my scale the weight sits at 102g with a bit of cable, so it’s most likely in the 100g range without the cable. Although this weight is still somewhat acceptable, the MM520 is notably tail heavy out of the box. The weight imbalance is mostly due to the internal weight that is installed per default. Luckily the weight can be fairly easily taken out (warranty isn’t voided by doing so), the screws sit below the lower and the right mouse feet. Removing the internal weight brings the weight down to roughly 87g without the cable (the weight and the screw weigh approximately 13g together), which is a competitive weight in this size category.
Unlike most other mice on the market the MM520 isn’t made of ABS but of PBT plastic which is supposed to be longer-lasting and of overall higher quality compared to ABS. In hand the MM520 indeed feels high quality and quite sturdy. The coating is nice to touch and fairly grippy; it’s also worth mentioning that it doesn’t attract dirt or finger marks as much.
The main buttons are separated from the shell. The clicks themselves are tactile and crisp with little to no pre-travel; due to the construction there is some post-travel, however. Personally I wasn’t bothered by this as I don’t push in the buttons as much, but it might be an issue for others. It’s also worth mentioning that my copy has an issue with the left click. Unlike the right click the left one is ‘loose’ and wobbles horizontally. I’m not sure whether this problem is widespread, but it doesn’t seem to be inherent to the construction (unlike with the buttons on the Rival/ Sensei 310, for comparison). The loose button didn’t bother me during play, but for office work it was a bit annoying. The side buttons have little pre- or post-travel, however they’re fairly hard to press in. The scroll wheel is quite excellent. It makes little noise in any direction and the steps are defined and tactile. (For those who are interested: An Alps encoder is used for the scroll wheel.) I also had no issues with accidental scrolls.
The cable is a standard rubber cable with above average flexibility. I’ve had no issues during use either with or without a mouse bungee. The default mouse feet are already a bit scratchy right out of the box but they glide well enough. Personally I see no need to replace them.
My copy has no rattle whatsoever.
Default CPI steps are: 400-1200-4000-12000. The actual (measured) CPI out-of-the-box, however, is 420-1280-4250-12800. Note that the margin of error increases with CPI. The lighting is already active OOTB which makes it easy to tell the CPI steps apart.
Not much to say about this, there is no visible sensor smoothing at 400 CPI out of the box.
Testing with the most recent firmware
There was no need to update the firmware as the latest one was already installed. I’ve set the nominal CPI to the common steps of 400-800-1600-3200. The actual (measured) CPI, however, was 420-845-1700-3370. This result is odd insofar another review showed a significantly lower deviation. Still, I can say with confidence that my numbers are accurate. I’m not sure what could be the reason for that disparity.
My copy of the MM520 already came with the latest firmware, therefore the results seen in the previous section are applicable in this one as well.
Still no visible sensor smoothing.
Still no visible sensor smoothing.
As expected from a 3360, smoothing (32 frames which translates to 6.2 ms of frame averaging) kicks in at and above 2100 CPI.
No unusual jitter, no angle snapping.
A 3 m/s swipe must do, but rest assured that the 3360 in the MM520 has the same sky-high PCS as every other 3360.
The software is rather interesting. First you need to install a hub software called Cooler Master Portal which allows you to manage several Cooler Master peripherals at once (in case you happen to own more than one). Then you need to specifically install a driver module for the MM520 that is accessible separately. The software itself is among the better ones I’ve seen. It’s fairly lightweight both in terms of disk space and memory usage and offers a decent range of options. There is not only the option to remap every button but also a functional equivalent to Logitech’s G-shift function called TactiX which allows you to assign every button with a secondary function upon pressing a specified shift button. Per default this shift function is assigned to the CPI switch button which can be used for cycling through the four CPI levels by clicking and as the shift button by holding the button.
The lighting includes two zones (scroll wheel and the underside of the mouse) that cannot be operated separately (or at least I couldn’t manage to do that). There are several lighting modes such as breathe, static or CPI switch; the colour accuracy is decent throughout. It’s also noticeable that you can get it to display a rather dim white which isn’t possible on every mouse. Although I personally don’t really care about RGB I do have to admit that the MM520 has rather beautiful lighting.
The internal memory of the MM520 is capable of storing up to four CPI levels. Unfortunately there is no way of deactivating one or several of them in case you only want to use a specific one. CPI can be adjusted in increments of 100. There is also the option to set the CPI for the x- and y-axis independently. The USB polling rate can be adjusted to 125Hz, 250Hz, 500Hz and 1000Hz. Being able to set a 125Hz polling rate can be useful for some older games so having that option is certainly a plus. All polling rates were stable on my system. An on/off toggle for angle snapping is available as well, the effect is rather tame though. Lift-off distance can be set to either low or high with ‘low’ being below 1 DVD and ‘high’ being between 1 and 2 DVDs on a cloth pad. There’s also the option to do a surface calibration for lowering LOD even further, but since it’s already low enough most people probably won’t need it.
There’s also an option that deserves some special praise. The debounce time (click delay) for the main buttons (M1/M2) can be adjusted in steps of 4ms from 4ms to 32ms, which enables one to either get a click latency almost on par with Logitech’s mice or a higher debounce in case you’re experiencing double clicking. I wish more companies would include this incredibly useful option in their software.
Finally, the software also offers macro functionality (which I didn’t test since I don’t use macros) and up to five profiles that allow you to quickly switch between entirely different setups.
I did notice a small bug: After uninstalling the software and restarting the PC for the first time, the OS cursor speed is set to maximum. On subsequent starts the slider stays at the set value.
Its unique shape makes the MM520 stand out for sure (along with the lighting – hats off to CM for the RGB on this mouse). Personally I had some troubles adjusting to the shape, but if the MM520 happens to suit your hand better than mine then you get a high quality mouse with barely any flaws (only the weight is a real flaw but this can be easily fixed by taking the internal weight out).
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