I bought a couple of these "large" 40mm arcade buttons to replace some standard buttons. Their mounting hole diameter is 25mm. They come with a mounting ring that holds the button above the surface -- needed to provide space for the button to travel, and I didn't want to be drilling an actual 40mm hole (with keyway) to let it mount flat to the surface. You can see what I mean with the first blue button image.

I didn't care for the vertical ring and it was taller than necessary. I printed up a slanted bezel that follows and extends the button's existing bevel which, I believe, looks better.

In addition, you can set some filament-change commands in your slicer and get concentric color rings in the bezel.

I slapped some red vinyl on a scrap board with a 30mm hole to show you what they look like installed.

I've included two bushings that I've found useful. While you can mount these 24mm buttons in a 28-30mm hole (where an existing button was removed, for example) the button swims around in the hole. You can use one of the bushings to reduce an existing hole size to 25mm - which fits this button perfectly. Just feed it in from the back - followed by the included nut to finish it up. I've also included a 28mm bushing in case your existing hole is drilled a bit smaller. They'll fit boards as thin as 1/2" - I use mine on a 3/4" MDF panel.

I've also included a slightly different bezel that reduces the bevel angle just a little with the result that the diameter of the base is a little smaller. This could save some room on a crowded control panel. This one is identified by "narrow" in the name.

Prusa

i3 MK3

No

No

.20

??

The very top layer on the bezel should slice to a single perimeter. If your extrusion width is the default it may be wide enough to be about the same as the previous layer, making it appear that the slope changed to 90 deg at the top, instead of printing a visually even slope. If it happens and it bothers you, try thinning the extrusion width a bit. I use .4 for outer perimeters on this model and that seems to do the trick.