Yes they are pretty much all 5/8" arbor, as Brew said, but usually the wire-wheels, etc, will screw straight on, instead of using the nut that you use to hold grinding discs on. Ive tried many brands and "supposedly" different quality of wire wheels, cups, and they all wore out at about the same rate...whether it was a $15 DeWalt or a $3 "made in Taiwan"-brand. I grew tired of digging wire-pieces out of everything in my garage until I finally found a variable-speed grinder (the 2 I had were heavy-duty, but were single-speed), cuz they clean just as well at a MUCH slower speed and the wheels and cups last much longer. Also, at slower speeds the wire doesnt imbed itself into your skin quite as deeply.
