Build Quality

Overall build quality is solid. There is a minor rattle from an indeterminable location when shaking the mouse. When applying lateral pressure, minor creaking but no flexing of the shell can be observed. Activating the side buttons by squeezing the sides is impossible. Lastly, no accidental clicks occur when slamming down the mouse irrespective of the set button debounce time.

Buttons

Main buttons on the M4 Wireless are very good. There is some pre-travel, but post-travel is low, resulting in a tight and snappy button response. Despite being visually separated from the shell, lateral button movement is minimal and needs to be provoked. Button stiffness is medium, though the buttons aren't entirely uniform as the left button is significantly stiffer than the right one. A set of Kailh GM 8.0 (80 M) switches is used.


Side buttons are good to very good. The back button in particular has noticeable pre-travel, but low post-travel, whereas the forward button has both low pre and post-travel. Button response is firm and pleasing. Button placement is good as actuation is possible quite easily by rolling one's thumb across. A pair of Huano switches (white plunger) is used for these.

At the bottom of the mouse is a single button for cycling through the available polling rates, which works just fine. The slider switches between off-state, CPI control, RGB control, and the PGDN bind. While fairly stiff, this slider too works just fine.

Scroll Wheel

The scroll wheel is very good. Scrolling down is slightly noisy, but tactility is on point, providing clearly discernible steps and controlled scrolling. The encoder comes from F-Switch (brown, black core) and has a height of 11 mm. The middle (scroll wheel) click requires medium to high force for actuation. Another switch from Huano (yellow plunger) is used for this one.

Surface

The M4 Wireless has a smooth matte surface all over. Grip is fine, and it doesn't attract fingerprints, dirt, or the likes too much. It is easy to clean, and there are no signs of wear left after doing so. All in all, excellent materials.

Button Sound Test

Disassembly

Disassembling the M4 Wireless is easy. First, remove all the skates and the screws beneath them. Top and bottom shell are easily separated now, though some caution ought to be paid not to rip the cable connecting side-button and main PCB. The internal design is rather simple. Top and side buttons sit on their own PCB screwed into the top shell and connected through a 4-pin connector. An auxiliary PCB sits next to the scroll wheel providing illumination and connects directly to the main PCB. Everything else is located on the main PCB, which, much like all the other PCBs, is very thin to save as much weight as possible. Three (possibly four) screws are used to affix the main PCB to the bottom. The MCU is a CompX CX52850.


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