Woodland Scenics considers the "coarse" to be O-scale. But that is all in the eye of the beholder. You will undoubtedly want to try and match up your Brummy's ballast based on the actual particle size range, as per the picture description.
I have heard numerous times that Woodland Scenics ballast is basically just crushed walnut shells. Although I have used quite a bit of their fine ballast (for N-scale), I have never actually verified this. I wouldn't be surprised, however, as their ballast is very light weight, compared to actual crushed rock ballast.
