As you know, drip irrigation is one of the most economical. This thing is a tap for drip-watering plants.
The water tap is designed to be connected to a 6-7 mm inner diameter with a silicone or rubber hose. The range of operation is approximately 1-100% of the opening. 0% of the opening can not be provided by such a design, however in my opinion the appearance is rather steep. However, 1-100% is quite a suitable range for drip irrigation.