Maintain proper water flow to your aquarium wet/dry filter overflow boxes. Rigid, plastic U-Tube is perfect as a replacement U-Tube or for custom aquarium plumbing projects. Large diameter U-Tube allows more water to pass through for efficient transportation of aquarium water. NEW 1" diameter Nano U-tube is perfect for smaller siphon overflow boxes. Available in 7-1/2" high x 1" diameter, 8" high x 1-1/4" diameter, and 8" high x 1-1/2" diameter.