They do, but I've had severe quality/lifetime issues with them. Three Kensington trackballs, two different models, all three lasted under a year for me.

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mkl 4 days ago | parent [-]

Strange. I have lots of Kensington Expert Mouse trackballs, some of which I have used for 7+ years, and none have ever given out on me. I have a stockpile of spares in case they stop making them, but they seem to be built very well.

Which models did you have problems with, and what went wrong?

	▲	lytfyre 2 days ago \| parent [-]
		Never tried the Expert Mouse in particular. Two of mine were slimblades, one orbit with scroll wheel. Different failures each time - Orbit - broken plastic around one of the bearings. ball no longer turned smoothly or straight in every direction, and dragged. Slimblade #1 - began to operate erratically. I believe it was a failure of some kind with one of the optical sensors, but I never was able to figure it out consistently. Slimblade #2 - microswitch under the LMB failed mechanically, no longer triggered. the slimblade's were provided by my employer at the time, the orbit was purchased personally for at home - it's use overlapped with the slimblades at work. I don't think I'm super unusually hard on my trackballs - My Elecom Huge lasted for ~6 years before the soft touch plastic finally got a bit gross from skin oil contact, but still was functionally fine, and my current protoarc is going strong two years in.