Basically, it's a box about 20 inches long and 12 inches square (inside
dimensions). This lets it fit over the end of my 10" with not too much
room to spare, so it actually stays put.
At one
end of the box is a foam core panel with a hole in it to accept the
light. There are some plastic hooks for little bungees to hold the light
in place.
About
seven inches away from the light (toward the other end of the box) is
the first diffuser. It is a piece of foam core with an 11" circular hole
cut out of it. The hole is covered with drafting vellum.
The
second diffuser is about seven inches further down the box, with the
same construction as the first. Here you can see what the second
diffuser looks like, looking in the other end of the light box: