Autogeek says they're slightly stiffer:
"We chose slightly stiffer hairs from a more mature animal than what you’ll find in our boar’s hair wash brushes. The increased firmness makes the bristles more effective at removing the tough grime that coats wheels, like stubborn brake dust. The hairs are thoroughly cleaned before being attached to the handles."
8 inch Montana Original Boar’s Hair Wheel Brush
I use a
different brand BHB for my wheels so I can't comment on if the Montana's are paint safe or not. I've never considered using my wheel BHB (I do have one unused on wheels) on the paint, perhaps because I have a normal (softer) BHB for washes when I decide to use it.