This item is used in the supply to any water using appliance such as filters, coolers, dishwashers etc. As it is 3/4" female x 3/4" male it simply connects inline with the hose.
In the event of more being used than it is set for, i.e. a leak, it will shut off the supply and prevent water damage.
The amount of water used can be adjusted when it is installed.

This product can give a lot of peace of mind for a modest cost.