Storm Water Leaching System, It Is A Structural Polyolefin Round Drywell System With UV Inhibitors, The Unit Contains 3 Side Panels, & 1 Top Panel, & It Fits 4" Sch-40, & 4" DWV Pipe, It Holds 40 Gallons, With 18 Each 1.5" Knockout Leaching Ports, & 3 Each 4.5" Knockouts Inlet/Outlet Ports Per Panel.