Just a warning - don't try to use them to clean fingers!
I made the mistake of wondering what it would feel like if I stuck my finger in my one years ago without really thinking about it. Result was me making a startled yelp that sent the cat into hiding for an hour and launching myself across the room. Felt like I'd had a nasty electric shock.
Thinking about it, the thing works by causing cavitation in the water around the thing being cleaned - when I stuck my finger in there it tried to do the same to the water in my finger. That hurt. So don't do it!
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