Half the height of the open space of the 13x11x7 box with pockets for small things like nuts, bolts, washers, etc.The STL previews, both here in Youmagine and Simplify3D may show pockets having their base missing, yet in FreeCAD they're there. A toolpath preview in S3D shows that the base will print properly, as can be seen in the photo.Cut at the height you require if you want a shallower tray.