Tuf Tite 20" flat septic tank lid is used in conjunction with the Tuf-Tite 20" septic risers. The flat lid is more substantial than the domed top and is structurally strong er as well. It will also fit most 20" IPEX- PVC ribbed pipe, and 20" Corrugated Pipe. We advise using the cad drawing below to make sure it will fit properly on your application. 2500 lbs load rating made from non-corrosive HDPE material. The lid is 20" ID 24"OD total.