This Fish Safe liner has a 20-year manufacturers guarantee. Cover the liner with stones & gravel and extend it's life expectancy indefinitely. 45-mil EPDM Pond Liners are economical and easy to install. This heavy duty black material has a 20 Year Limited Warranty and is FISH POND FRIENDLY. This liner is easy to work with, even in the most extreme temperatures. With EPDM Pond Liners you can make your pond any size, shape or depth and still keep a "natural" look. Fantastic for KOI FISH and GOLDFISH and many more water applications. A strong 45-mil EPDM liner is the best choice for most pond installations. Unlike concrete, it is easy and inexpensive to install and won't crack. When covered with stone, it has a 40-year life expectancy. If a leak ever were to occur, a simple inner-tube patch kit can make it as good as new. Let your imagination determine the shape of your pond! Available in 6 different sizes TJB-INC INSTALLATION TIP: At TJB-INC, we always use the 4 oz. Underlayment before the liner is installed. We had several bad experiences where we did not use underlayment and developed leaks in the stream liner when liner was walked on. Underlayment would have protected the liner from the sharp objects in the soil from puncturing the liner. So learn from our early mistakes, and protect your liner or wish later that you had! Browse through our TJB-INC Amazon Store for more Aquascape items.