Don't use them on the car either. The ends of the brushes are not so hard and certainly do not leave scratches in the paint. But what gets caught in the brushes after the first wash can be harder than the paint and scratch it.
The brush is for cars, but I decided not to use it on my car for fear of scratches. It is also too bulky for me and only good for larger, straight surfaces. Find a straight, soft brush like they have in the car wash boxes. That is my personal opinion.