HYDROMAXX 4 in. x 25 ft. Black PVC Schedule 40 Flexible Pipe 2202400025 - The Home Depot
Flexible PVC Tubing | 4 Inch Flexible Tubing | The Pond Guy
TerraBloom 4 Inch Aluminum Flex Duct - 25 FT Long, Flexible Ducting with 2 Clamps, 3 Layer HVAC Ventilation Air Hose - Great for Dryer, Grow Tent, Green Houses, Household HVAC Venting - Amazon.com