The harder outer shell ones, usually dark brown, and the softer whiter
colored ones. (I think these are called boisduvial scale).

There is also cottony cushion scale that's soft and mushy. Starts out
looking like a chip of paint. There may be some sap present. Easy to kill
with alcohol.

Am I the only one or does Bayer's product names all sound the same to
everyone else, too?

Ditto!

Diana