If you are thinking of replacing them, then buy 6mm replacements. The kits generally seem to have 6mm inlays, but as the kits come from several different factories, there's no guarantee they will all be 6mm.

But if you do end up with a kit with 5mm dots, you just drill out the hole from 5mm to 6mm and fit them.

And if you just want to fit vinyl dot (or similar) stickers over the kit inlays, then 6mm will cover both 5mm and 6mm dots.

6mm is the way to go.