The size of the ball in the trackball varies from as large as a cue ball, to as small as a marble. Mostly varies according to device and purpose.
Small (14-25mm): Mostly for keyboard built-in trackball, featured space-saving and general pointing use.
Median (34mm): The most common size for the majority of trackball mice in the market, featured suitable thumb-control size.
Large (55mm): Designed specifically for the precise pointing purpose. Bigger size supports multi-finger control at the same time.
Trackball mouse can be tailor-made to natural human palm shape the most, as it doesn’t have to consider movement design. With its ergonomic design, users can rest their hands on it comfortably for a long time use.
Also, as all movements are limited to fingers only, saving a lot of repetitive movements to other parts of the body from wrist to shoulder, so does the pains afterward.
Since it is a static device, instead of rolling the mouse on top of the table, trackball device can sit on any surfaces with different textures or spaces (e.g., a mobile workstation with limited space, or the softest pillow on your couch).