Cast Rattle

"Cast Rattle" is a very interesting puzzle. I got it as a gift from a friend, who was impressed by the design. When I first saw it, I was not that impressed by it, but in time my overall opinion changed.
The puzzle consists of four equal pieces. Each of them has a strange shape (not very appealing to me). They all four form that weird object, which is symmetrical on both sides (if you turn it upside down you can see the same structure). Once you have it in your hand and move any of the pieces, you will think that they are about to get separated. But the next moment any further movements do not allow it to happen and the puzzle stays assembled.
The concept for this puzzle is excellent! I solved it easily, because I have already solved "Cast Quartet" and I found one similarity. That helped me a lot, although some people might not agree with me that these two puzzles have anything in common.
The solution to "Cast Rattle" is very precise and... yes, there is a solution. All four pieces could be separated, scrambled and then put back together in any order - they are just identical in shape. Finding that solution is a matter of thinking. If you come up with the idea how to separate the pieces, it is a matter of time to apply it and succeed. I don't think it could be solved accidentally, unless you have great deal of luck.
My rating for "Cast Rattle" are:
Idea: 5
Implementation: 3 (personally, I don't like the shape of neither the puzzle nor each pieces separately, that is why so low rating; but I can't deny that the design is clever and intriguing; also, the used material is very pleasant - it seems to be the same as the one used for "Cast Quartet" but with different color outside, although I am not familiar with the real deal about these materials)
Experience: 4
Difficulty: 4
Overall: 4
Finally, I would recommend this puzzle to people who already have few easy puzzles in their collection. Say you have experience with solving 5 or 6 similar puzzles and you wonder what the next one to be - you might want to give this one a chance then.