Hello, drummers worldwide, I have a question. A friend of mine told me about a drummer seat which is (not reallly sure) filled with a sort of liquid and it should overfall when you're not sitting in a position natural to vertebra and subconsciously motivate you to sit in the right position. Should be the similar principle like the medical ball. Shame is I haven't found anything about it on the internet and the friend just saw it somewhere on a drummer exhibition. Do you know something about it and where to get it? Thank you a lot for the answers!