This 6 oz geo-textile underlayment material is extra strong and will protect you liner from tree roots or rock upheavals. Fast and easy to install. No other protective material needs to be used under the liner. Water and gas buildup under liner will be raised up and released by the underlayment. Underlayment comes in 15ft std widths, but we have broken it down for your convenience. You can piece underlayment together, so you could order multiples sizes if needed. Use under the major part of your pond and under streams. Excess underlayment (or liner) can be used to cushion extra large rocks if used on top of the liner in the pond.