... Protect pump (e.g. in wells) against no-load operation. Flow SwitchLight weight ,easy installation , ... or oil applied, without using filters.3. No wearing and fatiguing parts applied, featuring stable performance ... performance ,long life ,easy installation. 5. Switch contact start value for liquid flow: 3L/MIN ... :1/4`` 3/8`` 1/2`` 3/4`` 1`` O-12 1/2`` outside tooth Max switch rating :70w Max switch ...