What are the differences between these adjustable height desk models?

The Wallaby holds your Laptop or Monitor, Mouse and Keyboard on the 28 x 24 work surface and has a single vertical adjustment of 15 inches. All of The Kangaroo models hold your Keyboard and Mouse on the 28 x 24 work surface with the same 15 inch vertical adjustment, but they also have an additional 6.5 inch adjustment for your Laptop or Monitor which is held either by a shelf as on "The Kangaroo" or on one or two VESA mounts as on "The Kangaroo Pro" or "The Kangaroo Elite"

How does it attach to my desk?

All of our adjustable height desk models are completely free standing and require no drilling or clamping to your desk. It sits on your desk the same way your monitor sits on your desk and it is very easy to move by sliding it across your desk.

It looks like it might be top heavy. Will it fall over if it gets bumped?

All of our adjustable height desk units are very stable and they will not fall over. The base is made with a solid steel plate that weighs nearly as much as  the rest of the unit combined. There are  felt pads on the base for ease of sliding the unit as you desire. Truly, the only way these units can fall over is if you push it off your desk.