The Ultimate Pond Lining System was launched by Blagdon in 2011. It's aim was to take the worry out of choosing incorrectly sized pond liner underlay by putting the liner & the underlay in one bag. The liner in this pack is a popular size of 4x 3m (13' x 10') while the underlay is slightly larger to allow overlap at 4.4x 3.4m (14'4" x 11'2"). The thick (0.5mm) PVC Liner is guaranteed for life when used with the thick underlay supplied.