Vevor Pond Liner 15 x 20 ft. with Underlayment Leakproof 45 Mil Thickness NewThis pond liner combo includes a 45 mil EPDM rubber liner and a protective non woven underlayment for building outdoor ponds. It is designed to help reduce punctures, minimize water loss, and handle changing outdoor weather conditions. The flexible liner can be used for backyard ponds, landscape ponds, waterfalls, fountains, and fish habitats. Its tear resistant construction supports long term outdoor use and fits a variety of pond shapes.