Kensington Expert Mouse 1992
Ball diameter: 55 mm [see Trackball Ball Sizes and Replacement]
Since the 2000s, their market got eaten by Logitech Trackballs, and i think their product's quality and innovation also gradually declined.
I think one major problem is that the ball has a lot friction. I remember i tried it in stores and think the friction is the worst of all trackballs i've put my hands on.
Also, Kensington's classic design always seems unwieldy for me. That you have to bend your wrist up to use it. If i actually use this, i'll have to put a folded-towel in front to rest wrist on.
This trackball is notorious for not supporting Windows 7. ( update: Shadow Skill says Windows 7 driver has been released.)
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