Thanks for the full answer though.

"Actually the weight of the crown can make a sound difference. This difference is extremely small and usualy only a professional can tell the difference."

Thats funny, because I am a professional flutist and if there is a difference in sound, then it is so slight that I would not benefit from it.

I agree with you Kara!

Heinrich,
I posted my question about these rings on James Galway chat, asking if anyone had one of these and do they work?
James Galway replyed saying " I tried these rings and they do work. I think they work better on headjoints which are not top quality"
Look for yourself at the other postings.If he said they can work that`s good enough for me.
Anyway I tried to get one and cannot get a reply from the seller!