Yes, they are the ones with the "fingers".
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Yes, you have to buy an driver for them.
Yes, they can eat metal, if you use them like a grinder. That's why I said don't push down on them hard, and don't run the tool very fast. If you don't do those two things they are the best tool available. You can also seriously screw up surfaces with a scraper if you use it wrong. The thing I find most favorable is that with a sanding disc, or the scotchbrite style, then you can leave behind abrasive that can damage internal components. With the "rubber" ones, it's just hard rubber/plastic or whatever, so it won't damage anything. The material you are cleaning off is more abrasive.
I bought them from my Snap-On dealer for a long time. Then I asked my parts supplier if they could get them. They could for about $5 a piece cheaper. The little disc's are expensive for what they are. But like I said, when used properly they last forever. I've made one last several months and cleaned hundreds of parts. It's all in how you use them. Expect to pay anywhere from $7-$15 per wheel depending on where you get them. Napa, O'Reilly's and others can get them. They are usually cheaper per wheel if you buy a few at a time.