The maker of the Power Balance bracelet worn by many athletes has been forced to admit misleading advertising and to refund customers in Australia.
Power Balance admitted there was no scientific evidence for its claims the bracelet improved "balance, strength and flexibility".
It had been pressed by the Australian Competition and Consumer Commission (ACCC) to back up its claims.
Sportstars such as Shaquille O'Neill and Kevin Pietersen wear the bracelet.
"Suppliers of these types of products must ensure that they are not claiming supposed benefits when there is no supportive scientific evidence," said ACCC chairman Graeme Samuel.
"Consumers should be wary of other similar products on the market that make unsubstantiated claims, when they may be no more beneficial than a rubber band."
Power Balance has agreed to amend its website and packaging, as well as remove the words "performance technology" from the wristband itself.
It has also agreed to publish accurate advertising and refund customers who feel they may have been misled.