yes, the trackball is interchangeable. In my case, it made the trackball movement (physical) much smoother. please note that the ergonomics is a bit different from the wired version (in my opinion.

I just checked this and The red ball will work for the wireless, but the blue ball doesn't work in the wired. I don't feel a difference in the ball position between the two. Both fit my hand comfortably.

It'll fit, but just because you can doesn't mean you should.

I love my Marble Mouse (red ball) and have used it for many, many years, at work.

I don't know if the balls are interchangeable. The Trackball I got about a month ago is for home use.

The change of position for the ball makes a huge difference---the Trackball is a completely different mouse. I suspect that for all who are used to the Marble Mouse, this Trackball will be disappointing. I still use the Trackball, because I need a wireless mouse at home. But I don't at all have anywhere near the maneuverability that I have with the Marble Mouse. Which means the Trackball gives me none of the pleasure that I get from the Marble Mouse.

I too own a wired trackball and the wireless. The balls are NOT interchangeable. I highly recommend getting the wireless version. The ball placement made a huge difference because your thumb naturally moves quicker. Plus the design of the wireless is more comfortable.

This one is tiny, like 1/4 inch. Kind of hard to get out actually when I got my new one and had to switch receivers.

Not very much - I installed it on front panel and door still closes. I think it is maybe 3/8" or less.

BillC

ONLY STICKS OUT OF USB PORT ABOUT 1/2 AN INCH

Once it's plugged into the USB port, the bluetooth receiver only protrudes about 1/4".

I'll guess a 1/4 inch at the most.