The colors of the "balls" represent different grits, but they're all pretty close. Also useful for cleaning train wheels, wheel flanges, axles, wipers and other things I haven't thought of yet. They have a very thin shaft which some Dremel's will not close tight on, in which case you might have to buy an adaptor for the Dremel.
I'd try simply spreading the clearances a little where the pick-up flange sits in the pick-up frame, before removing it and bending it. In fact, if you have to remove it, I'd try lightly sanding or filing the edges/surface of the flange with a sanding wheel or stone using a Dremel, before bending it.
