Callaway Tour ix Golf Balls (12-Pack) The fastest growing ball on tour in 2010 Tungsten-Infused outer core distributes weight away from the center of the golf ball to increase the ball's moment of inertia Dual Core combines a lower compression inner core inside a higher compression outer core to manage spin New, softer thermoset urethane cover provides unmatched feel High density mantle layer works with the dual core to produce high ball speed and move more weight to the perimeter