Beckett Pre-Cut Pond Liner Underlayment BlackThis Beckett Pond Underlay is great for any pond, container garden, waterfall, or swimming pool. This underlayment ensures that things such as rocks, sticks, and rodents do not at all damage your liner, ensuring a long and healthy life for your pond and all of its parts. This underlayment liner is made of polypropylene, which is great for fish ponds as it creates an ecologically friendly environment for flora and fauna alike. The flexiblity of the