I realized that many people don't like the bases. Maybe they are not perfect, but in my opionen they are not to bad.
The diameter is close to a 25 mm washer as you can see on the picture above, might be 23 mm or 24 mm, so that should work for most cases.
The upside got different designs, like gravel for wild west and copplestone or other stone structures for towns folk.
This might be a help for people who don't want to spend to much time in designing the bases.
And if you dont like the structure which come with this on casted bases, you can easily change them.
Very often people put some glue and sand on a washer design the base (as I do). You can do that here as well and you won't see the structure anymore. To be very sure you could even smooth the upside with some milliput or something before.