Aquabuy 4 x Air line valves - Air line tap - 4mm tap (1/2 turn type)
The taps are a half turn from off to full on using a control knob
They are suitable for air and liquids and give easy control by rotating the knob,
they cannot be turned too far as they are limited to a half turn giving excellent control from full on to closed.
Actual taps may vary from the one shown in the picture.