Here’s some serious catnip for golf nerds. A top player—specifically, Rory McIlroy—is fussing around with not one, but two different training aids on the range of the DP World Tour’s BMW PGA Championship this week.

So what are these training aids?

What do they help with?

Why is Rory using them?

Great questions! Let’s break them down.

The saints at the DP World Tour captured four different videos of Rory using the training aids. In the first video, Rory is using the G-Snap, a training aid invented by Golf Digest Top 50 Teacher George Gankas.

The training aid snaps when you put your wrist into flexion, which helps golfers flatten or bow their lead wrist, as opposed to cupping it.

Rory says he tends to cup his wrist excessively on the backswing, but it can occasionally pitch the club across the line at the top of his backswing, which can cause him to miss left (as I wrote about following his U.S. Open heartbreak).

The G-Snap prevents this from happening. It puts a little more flex into his lead wrist, which puts more “strength” in his clubface, which is something Rory talked about working on with Butch Harmon earlier this year.

It’s a subtle improvement, though. He doesn’t want to overdo the move, which is what he’s demonstrating here.

After a few shots with this, Rory adds in the ball between his arms and takes some practice swings.

This training aid is a different way of working on the same general idea.

When Rory uses his wrists to roll the club open, he has to roll them back shut, which can be hard to time perfectly every time—which can, again, lead to a left miss.

The ball between Rory’s arms prevents this wrist roll through. With the G-Snap helping put his wrist in a better position on the way back, the ball is there to quiet and turn his body freely through.

Rory seems pleased with the results. At one point in the video, he tells his longtime coach Michael Bannon that he feels like he can fully release the club and not miss left.

This article was originally published on golfdigest.com