Hyrda Pools, HLCUSTOM 20X40 Cambridge Aquarius In-Ground Liner; 20 ft x 40 ft, 20 ft x 40 ft Rectangle. A pool liner is the most important part of your pool -- the part you'll see every day for the rest of your life! Choose a liner that compliments your personal style. This Cambridge liner offers rich, dark blue hues with splashes of gold that will create a dramatic look in your outdoor space.