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 PF-Nano. Use 1-1/4" U-Tube as replacement tube for PF-300, PF-800, and PF-1000 & PF-1200. Use 1-1.5” U-Tube as replacement tube for PF-1800.