The Mini Montessori tray is a convenient size for small activities such as lego or early stage sorting.
The tray is small enough that it could easily travel with you or, be exclusive to the car (that is how our's is used).
Also, a big plus about the Mini Montessori tray is that a regular sheet of printer paper can be cut to fit exactly for coloring, templates and other activities.
1 3/8" deep
We have tested this tray with two children that aren't particularly gentle on their things and it has held up without a blemish.