Rory McIlroy is using a new driver shaft this week at the U.S. Open, a prototype by Mitsubishi Rayon that is similar to the company’s Kuro Kage Silver shaft.

McIlroy was previously playing another prototype Mitsubishi shaft, a Diamana Prototype 70X, which had a similar balanced profile to the company’s 4th-generation Blue Board shaft, which is called the B-Series.

While the new shaft McIlroy is using looks nearly identical to Mitsubishi’s Kuro Kage Silver shaft that golfers can buy off-the-rack, it is made with different materials, according to a tour representative from Mitsubishi.

The Kuro Kage Silver shafts are made of graphite material that Mitsubishi calls “High-Density Prepreg,” which has more carbon fiber and less resin than the company’s previous shafts to give it more strength and feel.

McIlroy’s prototype shaft has the same profile as the Kuro Kage Silver, a stiff tip and mid section with a softer butt section, but the graphite is reinforced with Mitsubishi’s Elastic Titanium Fiber, which is an alloy comprised of Titanium and Nickel.

The alloy, also called “TiNi,” is used to create the company’s Bassara W-Series shaft that has been used on the PGA Tour by Matt Kuchar. According to Mitsubishi’s website, the TiNi fiber allows a shaft to “deform and then recover immediately to its original shape.”

Check out the photos below of McIlroy with the new shaft in Wednesday’s practice round. He plays the shaft in a Nike Covert Tour driver that is set to 10.5 degrees with a neutral face angle.

On a side note, Nick Watney has changed from a prototype Mitsubishi Kuro Kage Silver driver shaft that he has been using all season to the Mitsubishi White Board 83X shaft he used in 2012.

According to the source, Watney was also playing a Kuro Kage that uses the company’s TiNi alloy. That source tells us that we will be hearing more about McIlroy’s newest shaft in the coming weeks.