I can tell you that he used scrap wood from Home Depot, cut it/built it to fit inside our sensory table, and used a Hole Saw to drill the holes in the top. The funnels fit snugly into the clear tubing (all purchased at Home Depot) and simply rest on top of the rack.
|Funnel rack (yes, I need one more funnel/tubing)|
|Great for water play!|
|Dropping water beads into the tubing. The water beads didn't fit through the funnels, so we just used taped to secure the tubing.|
- AK (MESE, MECD)