Gordon Low 4x5m Greenseal EPDM Pond LinerSize: 4x5m 0. 75mm thick liner. Perfect for any medium and large sized garden ponds, large water features, ornamental lakes, and streams. GreenSeal EPDM pond liner is perfect for any medium and large sized garden ponds, large water features, ornamental lakes, and streams. It is a high quality product, which is made from synthetic rubber. It has exceptional physical properties which offer good flexibility, especially for the more intricate designs.