A flattened ball powder. When its Winchester its called "ball" and not spherical, because Winchester owns the term "ball". This is why other brans call it spherical. A lot can fit into a case. More than you will ever need. This makes this powder more dangerous if you make a reloading error.
This powder surprised us. You can actually get some pretty high performance out of this for such a fast powder, or should we say, "we did", with the 90 grain bullets. We like this powder a lot and would be happy if it was all we used for range time practice, or even shooting steel competition. It is not as clean as the name suggests compared to some of the "Cleaner" powers in its category, such as perhaps Accurate #2 or D032 from Lovex/Shooters World.