Balance Point - a small change makes a big difference.
We adjusted the center of gravity of the instrument ever so slightly so that it would feel lighter and more responsive.
The actual shape was modified to move the handle closer in towards the center. In addition the profile of the new handle brings your fingers to a point just past the geometric center. This allows you to "drive" the instrument with less moment of force. That's what makes it feel more responsive.
And finally we completely changed the layout of the jingles. Now they are grouped on the arc to react faster so that you get more sound with less effort.