Maeda Koki MK type WATER SIGNAL – Flow Indicator Water signal and Oil signal MK model produced by Maeda Koki in Japan, Oil signal and Water signal Model MK have a function for detecting minimal flow. MK water signal manufactured using an acrylic tube is limited to the use of 80 ℃ or less. (Flow switch of the product is limited to the use of 60 ℃ or less.)
I can see a flow at first sight
It is a rheoscope confirming fluid flow by the movement of transparent balls (or a float) in the jurisdiction.
I cannot confirm the flow quantity.
The installation direction does not matter
The posture when attach it as use a spring inside looks up and look down; and
I can perform sideways-facing freely.