I use similar hoppers for my wire cages. I make mine 6 squares x 6 squares (1/2" mesh) x however long I want them. I have a 6 square x 6 square (3 inch) top and bottom. The bottom is attached at 4 sides, but the top is only attached to one side (for a hinge). I just fasten a piece of copper wire in and around the non hinged side and through the bars of the cage (and twist the ends together).

If you were asking about making a modified version for a wire cage top, I might be trying that soon .