The R&A has revealed it had warned players three weeks ago that it was going to randomly test players on the COR (Coefficient of Restitution) of their drivers at this week's Open Championship at Carnoustie.
A total of 30 players were driver tested by the R&A on Tuesday afternoon.
“We take our governance role very seriously, not just on the Rules of Golf and amateur status, but also equipment standards, and we felt it was an appropriate next step to more actively seek to test players’ drivers straight out of the bag,” said Martin Slumbers, the R&A’s chief executive.
Paul Casey, Brooks Koepka, Jason Day and Henrik Stenson were among those tested, and according to reports, there were no violations during testing.
Rory McIlroy was quick to suggest his brand TaylorMade were being singled out "more than anyone else."
“A manufacturer is always going to try and find ways to get around what the regulations are. It’s a bit of an arms race,” said McIlroy.
While this is the first time ever in Open history where golf's governing body has tested drivers for any violations, the R&A did test drivers at a Japan Golf Tour event earlier this season.