Build Quality

Overall build quality is mostly solid. There is a very minor rattle when shaking the mouse. When applying lateral pressure, the whole left side can be pressed in quite easily, but not the right one. Furthermore, the top (battery cover) can be pushed in easily, too. Activating the side buttons by squeezing the sides isn't possible, however. Lastly, no accidental clicks occur when slamming down the mouse.

Buttons

Main buttons on the M4 Wireless are good. Both pre and post-travel are moderate, resulting in a slightly mushy button response, although click feel itself is firm and tactile. The buttons are visually separated from the shell and can be moved from side to side, but this needs to be provoked and isn't noticeable during regular use. A pair of Kailh GM 4.0 (60 M) switches is used here.


Side buttons are good to very good. Pre-travel is low, but the forward button in particular can be pushed in way past the actuation point. Button response is somewhat dull and muted. The pressure point is mostly even across the entirety of these. Button placement is great as actuation is possible very easily by rolling one's thumb across. A set of low-profile Huano switches (white plunger) is used.

At the top of the mouse is a single button for cycling through the set CPI steps, which works just fine. Another low-profile Huano switch (red plunger) is used for this one. A slider at the bottom switches between 2.4 GHz, Bluetooth, and off-state, which too works fine.

Scroll Wheel

The scroll wheel is very good. Noise levels are under control, and tactility is quite good, with clearly defined steps and a matching tactile feel when scrolling. The encoder comes from Kailh (black core) and has a height of 11 mm. The middle (scroll wheel) click requires medium force for actuation. A seemingly unbranded tactile switch is used here.

Coating

The M4 Wireless has a slightly rougher matte surface all over, which provides great grip. In addition to that, the sides feature a very fine riffle pattern, which adds further grip but isn't as prone to catching dirt as coarser patterns. It doesn't attract fingerprints, dirt, or the likes too much, is easy to clean, and there are no signs of wear left after doing so. The top cover is made out of PBT polymer, while the rest is the usual ABS. All in all, excellent materials.

Button Sound Test

Disassembly

Disassembling the M4 Wireless is easy. Remove all feet and the four screws beneath them, and the top shell will come off with ease. The internal design is equally simple. Everything sits on the very thin main PCB, aside from the equally thin side-button PCB screwed into the left side panel and connected through a ribbon cable. The sensor is using external illumination and its full designation is PAW3311DB-T2MU. Three screws in total are used to affix the PCB to the bottom. The MCU is a Texas Instruments CC2640R2F, whose datasheet can be found here. Production date for the side-button PCB is the 30th week of 2021.


As for the soldering and general quality of the PCB, I'm unable to find any noteworthy flaws.