Build Quality

Overall build quality is solid. When shaking the mouse, a rattle comes from an indeterminable location. When applying lateral pressure, no creaking or flexing of the shell can be observed. Activating the side buttons by squeezing the sides is impossible. Lastly, accidental clicks do not occur when slamming down the mouse, unless the debounce time is set to minimum.

Buttons

Main buttons on the Hati-S Plus 4K are good to very good. There is some pre-travel, but post-travel is low on either button, and button response firm and snappy. That said, the left button on my copy emits a rather unpleasant "thock" sound upon release depending on the angle it is actuated at. As such, this occurs infrequently and mostly unintentionally, and interestingly enough, it disappeared after disassembly. While the buttons are visually separated from the shell, lateral button movement is minimal even when provoked. Button stiffness is medium to light. A pair of Zippy DF3-P1L1 (60 M) switches are used.


Side buttons are very good. Both pre and post-travel are low on both buttons, resulting in a snappy and pleasing button response. Unlike on the ACE, the back button cannot be pushed in as much. The pressure point is even across the entirety of these. Button size and placement are good, as actuation is possible rather easily by rolling one's thumb across. A set of low-profile switches from TTC (blue plunger) is used for these.

At the top of the mouse is a single button for cycling through the set CPI steps, which feels good. A switch from Huano (white plunger) is used for this one. The on/off-switch at the bottom can only be accessed by using a tool such as the included plastic stick.

Scroll Wheel

The scroll wheel is very good. Noise levels are elevated, but tactility is great, providing very distinct steps and controlled scrolling. The encoder comes from TTC (gold) and has a height of 12 mm. The middle (scroll wheel) click requires high force for actuation. An elevated switch from Huano (red plunger) is used here.

Surface

The Hati-S Plus 4K has a smooth matte surface all over. Grip is fine, and it doesn't attract fingerprints or dirt 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 Hati-S Plus 4K is easy. First, the front and rear skates along with the screws underneath them need to be removed. The sides are additionally locked in with clips, which are dislodged quite easily. When doing so, make sure not to rip the cable connecting the PCBs.

The internal design is efficient. The CPI and side buttons sit on their own PCB screwed into the top shell and are connected through a ribbon cable to the main PCB. The battery sits on a foam pad glued to the bottom shell. Everything else sits on the main PCB, which has been extended at the sides to help with shell rigidity. All PCBs are very thin to save as much weight as possible. Four screws in total are used to affix the main PCB to the bottom shell. The MCU is a Nordic nRF52840, whose datasheet is found here. The Bluetooth capability of the chip remains unused.


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