Trackballs come in two major styles, top ball and side (thumb) ball, this Deft Pro is the latter one. Admittedly I am still using trackballs! If you can remember them, the Trackball Explorer 1.0 from Microsoft to be precise.
And they are great to work with, Asia based Elecom will release a version that resembles that old Microsoft one a bit, the DEFT PRO.
Elecom's new trackball "DEFT PRO" has been redesigned and will be released this month. It is wireless over 2.4 GHz WIFI or Bluetooth and even wired connection by USB with an attached receiver. A rubber ring sits in the middle of the silver wheel providing a nice grip. The wheel functions as the middle mouse button as expected and also tilts up and down which would be left and right were it the traditional position on top of the body. The unit uses Omron switches with 10 million times endurance. There are 8 buttons including a "forward / back" button and a tilt wheel that supports left and right scroll, and the thumb operation area is substantial. DPI count can be switched in three stages 500/1000/1500 by a button.