Yoga, Meditation and Singing Bowls

I was at the Y the other day and ran into a friend of mine who takes all sorts classes like pilates and yoga and the like.
She was trying to get me to join in one of the classes, but I just don't have the time right now.
She started telling me about how great she feels after yoga and all about the meditation and aromas and sounds that help heal and relax.
It was very interesting.
I happened to look online and found a web site that has Crystal Singing Bowls and it has a little bit of info about them.
They must be something dear to yoga people because they have a sale going on right now and it saves you like almost 50 per cent on retail costs.
They range from 6 inch bowl to 20 inch bowl and it says the larger bowl rings longer at a lower pitch.
I think I may do some more research on what the sounds can do to help healing processes.
Anyone ever use these bowls?
I would like more info on them.