Rory McIlroy has a chance to join the most select group in all of golf – a career grand slam winner. With a win today at the 82nd Masters, McIlroy would join Jack Nicklaus, Tiger Woods, Gary Player, Ben Hogan, and Gene Sarazen as one of only six players in history to win all four of golf’s major championships.

Fans haven’t seen the feat accomplished in 18 years, when Woods won the 2000 Open Championship after already having won the 1997 Masters, 1999 PGA, and 2000 U.S. Open.

Here are 12 things to know about the Grand Slam:

1. Grand Slam Season: A traditional grand slam is winning all four major championships in one season or a calendar year. Some argue that winning all four titles consecutively is also a grand slam. Tiger did this in 2000-01, winning in order the: 2000 U.S. Open, 2000 Open Championship, 2000 PGA, and 2001 Masters.

2. Two Eras: Prior to the creation of the Masters Tournament (1934), the national amateur championships of the U.S. and the UK were considered major championships. During that earlier era, the Grand Slam comprised consecutive victories at the U.S. Amateur, British Amateur along with the U.S. Open and the Open Championship.

3. Career Grand Slam: As time went on, and golf became more global and more competitive, the idea of a player winning all four majors in a single season became an unrealistic goal, so the career grand slam took its place as something hard to accomplish, but more realistic to shoot for.

4. Bobby Jones: Ironically, the man who helped create the modern day grand slam by introducing the Masters, is the only one to have ever completed the true Grand Slam (1930) – winning all four majors in a single year. No man has ever achieved a modern era season Grand Slam.

5. Gene Sarazen: When Sarazen won the Masters in 1935 he had no idea he’d become a grand slam winner, as the Masters was a new tournament created by Jones, and years away from being designated a major and part of the grand slam.

6. Ben Hogan: As with Sarazen, when Hogan won the British Open in 1953, he didn’t know he’d completed the career “grand slam” as it was years away from being designated as such. In fact the PGA and British Open played the same weekend in 1953.

7. Arnold Palmer: After winning the Masters and U.S. Open in 1960, Palmer promoted the idea of replacing the amateur/pro grand slam with a modern day professional grand slam. “I said casually over my drink, ‘why don’t we create a new Grand Slam?,” wrote Palmer in his book, A Golfer’s Life. “‘What would be wrong with a professional Grand Slam involving the Masters, both Open championships, and the PGA Championship?’” Palmer’s idea helped align the four major championships as an elite pro series. Palmer would not complete the slam in that historic 1960 season, and ironically he would not complete it in his career – missing the PGA.

8. Select Company: Of the thousands of golfers who have teed it up as a professional golfer, only five have ever won all four major titles. And only three are alive today, as Ben Hogan (1997) and Gene Sarazen (1999) have passed on. Rory would be one of only four men walking on this planet to own all four titles. Heady stuff.

9. Current Players With Grand Slam Aspirations: Along with McIlroy, Jordan Spieth and Phil Mickelson also have a chance to join this select group later this season. Mickelson needs a U.S. Open title (Shinnecock Hills GC) to complete the slam, while Spieth is missing a PGA Championship (Bellerive CC) title.

10. It’s Hard: Given the fact that only five people have ever completed the slam tells you how difficult it is. And if you need further proof, of the current crop of top players in the world rankings, other than the aforementioned Spieth, Mickelson, and McIlroy, nobody else has won more than one of the four titles: Dustin Johnson (U.S. Open), Justin Thomas (PGA), Jon Rahm (None), Justin Rose (U.S. Open), Hideki Matsuyama (None), Rickie Fowler (None), Sergio Garcia (Masters), Bubba Watson (Masters), and Jason Day (PGA).

11. Legends Who Won 3 of 4: Some of the game’s most iconic players came up one title short, including Walter Hagen (Masters), Lee Trevino (Masters), Sam Snead (U.S. Open), Byron Nelson (Open Championship), Raymond Floyd (Open Championship), Tom Watson (PGA Championship), and Palmer (PGA Championship).

12. Multi Slams: Jack Nicklaus (18) and Tiger Woods (14) own a combined 32 career majors and each has won the career grand slams three times. Woods would need one more U.S. Open and Open Championship to complete No. 4. Nicklaus was one Open Championship short to complete four of them. Ironically, both Nicklaus and Woods completed their first grand slam at the Open Championship (Nicklaus ’66 Muirfield, ’00 St Andrews).

TIGER WOODS (3)
1. 97 Masters, 99 PGA, 00 U.S., 00 OPEN
2. 00 PGA, 01 Masters, 02 U.S., 05 OPEN
3. 02 Masters, 06 OPEN, 06 PGA, 08 U.S.

JACK NICKLAUS (3)
1. 62 U.S., 63 Masters, 63 PGA, 66 OPEN
2. 65 Masters, 67 U.S., 70 OPEN, 71 PGA
3. 66 Masters, 72 U.S., 73 PGA, 78 OPEN