The Orbit Trackball’s a little smaller in dimension than most trackballs, including Kensington's own Slimblade Trackball. You'll still need a fair amount of desk space put aside for it, but unlike a regular mouse you won't need to move it at all, giving it somewhat fixed dimensions.
We say "somewhat fixed dimensions" because Kensington supplies a soft rubber wrist rest with the Orbit Trackball. It doesn't so much affix to the base of the Orbit as pretty much just sit there plopped onto the base, but again, as a trackball this isn't a particular problem as all the moving parts are contained around the bright blue trackball itself.
The design of the Orbit ball makes it stand out from the trackball crowd, which traditionally goes for a bright red design that usually ends up giving off a distinct Hal 9000 vibe. The electric blue tinge of the Orbit ball has more of a low-budget fan-made Star Trek film feel to it, if that's your sort of thing.
The Orbit Trackball uses a single red optical sensor to detect the movements of the blue sphere itself, flanked by two standard mouse buttons. Unlike the Slimblade, there's no additional buttons on offer here, although you can define an action for both mouse buttons pressed simultaneously. Those who don't like messy cables may be annoyed by the fact that the Orbit is tethered by a USB cable.