They are made by a company called "Rhythm in jump. dancing close to you!" and preserve the fragile harmonics that are usually lost in a crystal lattice. They are known to be excellent... Buy them quickly and you can flip them to a collector.
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hahahha :lol: I cannot stop laughing, really, good one! :lol:
All joke aside, I definitely woulnd`t be bother with them. Wouldn`t be suprised if they would be home-made by someone who had too much time and spare soldering gun :D
For 40 euro you can find something decent on ebay or somewhere, really. Avoid them.