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not on the premier john they have an adjusting screw to zero
works the same as any gauge all ways test from the blue side connection the diffence is as the fluid is heavier than water the scale is smaller
plus points are it will never blow out the top and virtually spill proof
minus point is the price of the fluid but i use under £20 a year so not that sad
Mine's the 120mbar one, scale moves on that one. You're right about the fluid though.
Oooh get you! Size isn't important, you know! 😀
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