Procare 2 Ltr Serres Suction Liner x 24 Serres liners are made from extremely strong polyethylene and polypropylene. Latex Free. Manufactured to the highest standards they are subjected to rigorous testing during and after manufacture, including: - Liner durability and welded joints are tested by pressurising the liner and immersing in liquid. - The ability of the liner to hold a vacuum is tested by applying a vacuum on all components for 5 minutes, whilst long-term testing is conducted in the same way for a period of several days. - In a drop test, the liner is filled with 2 litres of water and dropped from a height of six metres onto a concrete floor.