Watering spike with cap connector for standard water bottle 500ml.

The cap has a hole and the adjustable shutter to regulate the flow.

You can also put a small piece of paper towel between the shutter and the hole, or even completely replace shutter with the paper towel to adjust the water flow to your liking.

Tip#1: you need to make a small hole at the bottom of water bottle to allow air inside.

Tip#2: to assemble shutter and cap use pliers or something that can press it evenly down, it's a tight fit between shutter and the pin.