If you're watching the Ryder Cup this week, you might notice the bags of the European players have different numbers embroidered on the front of them.
World No.1 Jon Rahm, for example, is represented by the number 161. Rory McIlroy is 144. Lee Westwood is 118.
It might seem random at first but it turns out there's a perfectly simple - and brilliant - explanation for it.
Speaking to the media at Whistling Straits on Tuesday, Rory McIlroy, who is preparing to make his sixth appearance in the match, explained the significance of the digits.
"There's been 164 players that have played for the European Ryder Cup team, or GB&I way back in the day," said the Northern Irishman. "It's a small collection of people that have played for Europe in the Ryder Cup. I think that's what brings us very close together, and that's been one of our sort of big focus points this week is just being here is very special and being part of a European team.
"Very few people can call themselves a European Ryder Cup player."
McIlroy added that numbering the players - commonplace in rugby union - had been captain Padraig Harrington's idea.
"He played a video for us last night to put it into context," he continued. "Only 570 people have been into space; I think over 5,000 people have climbed Everest; 225 have won a men's major.
"When you sort of break it down like that it's a pretty small group and it's pretty cool."
Here's the video in question: