I've never heard of these things and was expecting the worst clicking through to the site someone else linked.

But there's a version that seems reasonable at $100, that's not so bad. Then I looked at the other models and, yeah that's a very expensive soup can.

This thing is pretty, easy to use, and it produces an acceptable result..... but it's an expensive gimmick.

If you've got regular stones already and know how to use them, don't bother trying to replace them with this.

Something about working a blade edge-up is also deeply disconcerting.