Tensile strength is a measurement of how far a material will stretch before it snaps, like a rubber band. It's used for stretchy, unreinforced materials like EPDM. The problem with this test is that you don't really want to base your liner choice on when it's going to snap. What could you even do with a snapped liner?
A better "real world" metric for pond liners is grab tensile, which simulates the force of a sharp rock or heavy boulder trying to punch through or pull on the liner. For RPE, it measures how the reinforcing scrim and coatings work together to resist that force. A high grab tensile rating demonstrates that the material will resist tearing under the weight of your pond's rock work, which is a much more useful indicator of quality that how far it can stretch.
