Especially robust metal-plastic production. Simply connect the Suction Filter to the Suction Hose sold by the metre (Art. No. 1720-22/1721-22). It protects against impurities and thereby damage to the pump. The backflow preventer shortens the re-suction time and thereby allows more efficient pumping. Complete with hose clamp for easy securement. For Suction Hoses with a diameter of 19 mm (3/4") or 25 mm (1").