A: Id define it as pretty course.
A: Not truly a direct answer but doubtful a true stainless, a magnet sticks. My guess same as most wire brushes some sort of coated metal or spring type wire/steel because it holds up to pretty rough use doing a set of 4 old rusted Toyota steel rims. I've had and used it over the past 2-3 years stored in a unheated garage and no rust so possibly knowing this may help you decide.
A: Yes, this product is ideal for use on a drill. Thanks for the terrific question!
A: The width of this product is 4.61 in.