PondXpert Flexiliner is the UK’s top selling liner. Pondkeepers love it because it is tough and highly durable yet easy to lay and form into shape. The 4m x 4m liner (13′ x 13′) is a very popular choice. This flexible liner is manufactured around a triple-core process. A tough inner layer of tightly woven LDPE fabric is laminated on both sides with a UV resistant coating.