Supervike, thank you for the compliment.
Ultra, the bases is the standard 40 x 40 MM size. That's why I like the Pendraken miniatures so much - they fit the bases for HOTT, but still look OK with hte 15 MM figures.
To give an idea of scale, Here is a picture of an Irregular 15 MM A7V on a 40 x 80 MM base, and a Pendraken 10 MM A7V on a 40 x 60 MM base. I could fit the smaller A7V on a smaller base but try to keep bits from sticking out over the edge that might break easily. And HOTT does allow for deeper bases if necessary as long as the frontage is consistent.

Terry