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. Use 1" U Tube as replacement tube for Eshopps Overflow Box Model PF Nano. Use 1 1/4" U Tube as replacement tube for Eshopps Overflow Box Models PF 300, PF 800, and PF 1000 & PF1200.