Coconut Coir is a natural fiber made from the husk of ripe coconuts. These liners are designed to hold soil and plants inside trough planter boxes. This type of liner provides healthy water retention in your plant soil, while still providing proper aeration and drainage. This promotes root growth and healthy, beautiful plants. So easy to use, as these durable liners are pre-formed to simply drop into your 36-inch trough planters.