What putter was Tiger Woods using in the Masters?

He was using the newest version of the Nike Method putter. The last author was right in that the groove depth was reduced for Tiger specifically because the ball was coming off the face of the putter with too much speed. He used an older version of the Method putter in last year's British Open citing slow greens for the switch from his usual Scotty Cameron Newport #2, but switched back after because the ball was coming off too fast.