I am a huge fan of rugged boxes, but I could not find one for my Logitech MX Master mouse. I tried the rugged box for the Logitech MX Master 3, but my mouse just did not fit. So I decided to make my own one. This one works for the original MX Master as well as the MX Master 2s. I also made a small hole where you can potentially store a USB cable. 

Print settings which worked for me: 

3 perimeters

15% infill

0.28 layer height

No supports

Material:

The box and lid can be printed in PLA; for the latches and seal, I recommend PETG and TPU, respectively.

For the hinges, you need 6 M3X25 hex screws.

Text:

I also added a version with text. I printed this text first and let it stay on my printer bed, and then I printed the lid (version with a cutout for the text) over it. Make sure z-lift is enabled and turn bed probing off during this lid print. If you don't want this hassle, you can also print the version without text or glue the text on later. 

Fitment :

In my case, the mouse almost fits perfectly. However, I did not give it any more clearance because I was afraid the mouse would rattle and move inside, and now it just fits snugly without damaging the mouse or having the mouse move inside the case.  

Update:

I added a second version of the Box itself, one with a bigger cut out for a usb cable.