Tiger Woods uses a specially made golf ball in major championships, one not available to the public and not for sale despite his advertising endorsement. Nike's revelation that its Tour Accuracy ball is not the one played by this year's US Masters, British Open and USPGA winner comes as a result of a lawsuit taken in California by a public interest group.

The lawsuit by Public Remedies Incorporated contends Woods is involved in unfair labour practices because the ball he endorses for a huge fee is not the same one available to the public. It is the same principle as advertising a washing machine on television and selling the public a completely different but look-alike model.

Nike Golf marketing director Mike Kelly said the balls created for Woods have inner and outer cores that are "slightly firmer" than those sold to the general public. Kelly called it "industry practice" to tweak the designs of products made for the general public. Woods, known for his long-flying drives, used the Nike ball for his three major championship triumphs after previously playing rival Titleist.

A Titleist spokesman said the ball Woods once used was the same as anyone could purchase.