With tungsten in the face, the centre of gravity can be positioned further forward, which leads to more stable contact with less twisting on off-centre hits. This produces straighter putts and fewer misses if you aim correctly. The 2135 technology, where you have the sightline at a height of 21.35mm from the ground, is the exact middle of the ball and the optimal location for a sightline. This makes it easier to aim no matter how you set up your putts. The sightline never moves in relation to the ball, regardless of whether your eyes are directly above, behind or in front of the ball.