The Kensington Expert Mouse doesn’t really matter how large it is.  Except that it is a large computer mouse alternative.  Significantly larger than the Logitech Marble Trackball, although not significantly larger than my 6 x 8 mouse pad.  I love the wrist rest!  You can rest your wrist.  And this trackball has a scroll ring!  (Unlike the Logitech Marble.)  I can’t live without my scroll.

The scroll ring actually has weak “ridges”, but it stops after every scroll (even if you move it continuously, it scrolls then stops then scrolls then stops), so it’s very easy to scroll precisely.

It’s amazingly accurate!  Especially when you slow it down.  Because you can always “throw” the ball, or spin it hard, but you don’t want to waste your finger strength controlling an unwieldy ball, so it’s best to set it low and slow.  Plus, you can release the ball at any time, and it stays put, unlike a regular mouse, so that also makes it accurate.

Still, I can’t speak entirely for trackballs.  It definitely takes some getting used to using your fingers that much.  It’s not something you could take right into the office, you would have to practice at home first.

The scroll ring has good and bad aspects.  One bad thing is the extremely faint ridges.  But a good thing is you can scroll continuously by moving four finger all round the ring, and over the top, and down the other side, and up again, continuously circling around the ring.  That’s convenient for long documents.

It’s also nice that, if you’re like me, the regular scroll direction (on the right side, moving the ring upward goes up the document, and downward goes down).  Because that’s where my middle finger or ring finger rests.  And your thumb is on the left click, and ring finger or pinkie on the right click.

It’s a big, open-hand “grip”, really not a grip at all, just an open hand placement.  It’s very ergonomic, in the sense that it doesn’t use the wrist like a regular mouse, so you can rest the wrist.  It’s really nice after a long day of using a regular mouse.

Altogether a great mouse, if you’re looking for mouse alternatives.  $100 on Amazon.