I'm pretty sure I have a box similar to these at home.
I think they are referred to as heavy-duty cutting wheels, for a Dremel. If I remember, they are less adept to chunk apart and fly into your face, as you're cutting at an arc and the back part of what you're cutting digs into the wheel.
Wear eye protection.
You have to remove more material than with the thin ones, so overall speed of your job slows down, but they last longer.